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The Variation of Animals and Plants under Domestication by Charles Darwin

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Indies (21/17. G. Lewis 'Journal of Residence in West Indies' 'Home and Col.
Library' page 100.) it is said that "the only horned cattle fit for work are
those which have a good deal of black in them. The white are terribly
tormented by the insects; and they are weak and sluggish in proportion to the

In Devonshire there is a prejudice against white pigs, because it is believed
that the sun blisters them when turned out (21/18. Sidney's edition of Youatt
on the 'Pig' page 24. I have given analogous facts in the case of mankind in
my 'Descent of Man' 2nd edition page 195.); and I knew a man who would not
keep white pigs in Kent, for the same reason. The scorching of flowers by the
sun seems likewise to depend much on colour; thus, dark pelargoniums suffer
most; and from various accounts it is clear that the cloth-of-gold variety
will not withstand a degree of exposure to sunshine which other varieties
enjoy. Another amateur asserts that not only all dark-coloured verbenas, but
likewise scarlets, suffer from the sun: "the paler kinds stand better, and
pale blue is perhaps the best of all." So again with the heartsease (Viola
tricolor); hot weather suits the blotched sorts, whilst it destroys the
beautiful markings of some other kinds. (21/19. 'Journal of Horticulture' 1862
pages 476, 498; 1865 page 460. With respect to the heartsease 'Gardener's
Chronicle' 1863 page 628.) During one extremely cold season in Holland all
red-flowered hyacinths were observed to be very inferior in quality. It is
believed by many agriculturists that red wheat is hardier in northern climates
than white wheat. (21/20. 'Des Jacinthes, de leur Culture' 1768 page 53: on
wheat 'Gardener's Chronicle' 1846 page 653.)

With animals, white varieties from being conspicuous are the most liable to be
attacked by beasts and birds of prey. In parts of France and Germany where
hawks abound, persons are advised not to keep white pigeons; for, as
Parmentier says, "it is certain that in a flock the white always first fall
victims to the kite." In Belgium, where so many societies have been
established for the flight of carrier-pigeons, white is the one colour which
for the same reason is disliked. (20/21. W.B. Tegetmeier 'The Field' February
25, 1865. With respect to black fowls see a quotation in Thompson 'Nat. Hist.
of Ireland' 1849 volume 1 page 22.) Prof. G. Jaeger (21/22. 'In Sachen
Darwin's contra Wigand' 1874 page 70.) whilst fishing found four pigeons which
had been killed by hawks, and all were white; on another occasion he examined
the eyrie of a hawk, and the feathers of the pigeons which had been caught
were all of a white or yellow colour. On the other hand, it is said that the
sea-eagle (Falco ossifragus, Linn.) on the west coast of Ireland picks out the
black fowls, so that "the villagers avoid as much as possible rearing birds of
that colour." M. Daudin (20/23. 'Bull. de la Soc. d'Acclimat.' tome 7 1860
page 359.), speaking of white rabbits kept in warrens in Russia, remarks that
their colour is a great disadvantage, as they are thus more exposed to attack,
and can be seen during bright nights from a distance. A gentleman in Kent, who
failed to stock his woods with a nearly white and hardy kind of rabbit,
accounted in the same manner for their early disappearance. Any one who will
watch a white cat prowling after her prey will soon perceive under what a
disadvantage she lies.

The white Tartarian cherry, "owing either to its colour being so much like
that of the leaves, or to the fruit always appearing from a distance unripe,"
is not so readily attacked by birds as other sorts. The yellow-fruited
raspberry, which generally comes nearly true by seed, "is very little molested
by birds, who evidently are not fond of it; so that nets may be dispensed with
in places where nothing else will protect the red fruit." (21/24. 'Transact.
Hort. Soc.' volume 1 2nd series 1835 page 275. For raspberries see 'Gardener's
Chronicle' 1855 page 154 and 1863 page 245.) This immunity, though a benefit
to the gardener, would be a disadvantage in a state of nature both to the
cherry and raspberry, as dissemination depends on birds. I noticed during
several winters that some trees of the yellow-berried holly, which were raised
from seed from a tree found wild by my father remained covered with fruit,
whilst not a scarlet berry could be seen on the adjoining trees of the common
kind. A friend informs me that a mountain-ash (Pyrus aucuparia) growing in his
garden bears berries which, though not differently coloured, are always
devoured by birds before those on the other trees. This variety of the
mountain-ash would thus be more freely disseminated, and the yellow-berried
variety of the holly less freely, than the common varieties of these two

Independently of colour, trifling differences are sometimes found to be of
importance to plants under cultivation, and would be of paramount importance
if they had to fight their own battle and to struggle with many competitors.
The thin-shelled peas, called pois sans parchemin, are attacked by birds
(21/25. 'Gardener's Chronicle' 1843 page 806.) much more commonly than
ordinary peas. On the other hand, the purple-podded pea, which has a hard
shell, escaped the attacks of tomtits (Parus major) in my garden far better
than any other kind. The thin-shelled walnut likewise suffers greatly from the
tomtit. (21/26. Ibid 1850 page 732.) These same birds have been observed to
pass over and thus favour the filbert, destroying only the other kinds of nuts
which grew in the same orchard. (21/27. Ibid 1860 page 956.)

Certain varieties of the pear have soft bark, and these suffer severely from
wood-boring beetles; whilst other varieties are known to resist their attacks
much better. (21/28. J. De Jonghe in 'Gardener's Chronicle' 1860 page 120.) In
North America the smoothness, or absence of down on the fruit, makes a great
difference in the attacks of the weevil, "which is the uncompromising foe of
all smooth stone-fruits;" and the cultivator "has the frequent mortification
of seeing nearly all, or indeed often the whole crop, fall from the trees when
half or two-thirds grown." Hence the nectarine suffers more than the peach. A
particular variety of the Morello cherry, raised in North America, is, without
any assignable cause, more liable to be injured by this same insect than other
cherry-trees. (21/29. Downing 'Fruit-trees of North America' pages 266, 501:
in regard to the cherry page 198.) From some unknown cause, certain varieties
of the apple enjoy, as we have seen, the great advantage in various parts of
the world of not being infested by the coccus. On the other hand, a particular
case has been recorded in which aphides confined themselves to the Winter
Nelis pear and touched no other kind in an extensive orchard. (21/30.
'Gardener's Chronicle' 1849 page 755.) The existence of minute glands on the
leaves of peaches, nectarines, and apricots, would not be esteemed by
botanists as a character of the least importance for they are present or
absent in closely-related sub-varieties, descended from the same parent-tree;
yet there is good evidence (21/31. 'Journal of Horticulture' September 26,
1865 page 254; see other references given in chapter 10.) that the absence of
glands leads to mildew, which is highly injurious to these trees.

A difference either in flavour or in the amount of nutriment in certain
varieties causes them to be more eagerly attacked by various enemies than
other varieties of the same species. Bullfinches (Pyrrhula vulgaris) injure
our fruit-trees by devouring the flower-buds, and a pair of these birds have
been seen "to denude a large plum-tree in a couple of days of almost every
bud;" but certain varieties (21/32. Mr. Selby in 'Mag. of Zoology and Botany'
Edinburgh volume 2 1838 page 393.) of the apple and thorn (Crataegus
oxyacantha) are more especially liable to be attacked. A striking instance of
this was observed in Mr. Rivers's garden, in which two rows of a particular
variety of plum (21/33. The Reine Claude de Bavay 'Journal of Horticulture'
December 27, 1864 page 511.) had to be carefully protected, as they were
usually stripped of all their buds during the winter, whilst other sorts
growing near them escaped. The root (or enlarged stem) of Laing's Swedish
turnip is preferred by hares, and therefore suffers more than other varieties.
Hares and rabbits eat down common rye before St. John's-day-rye, when both
grow together. (21/34. Mr. Pusey in 'Journal of R. Agricult. Soc.' volume 6
page 179. For Swedish turnips see 'Gardener's Chronicle' 1847 page 91.) In the
south of France, when an orchard of almond-trees is formed, the nuts of the
bitter variety are sown, "in order that they may not be devoured by field-
mice" (21/35. Godron 'De l'Espece' tome 2 page 98.); so we see the use of the
bitter principle in almonds.

Other slight differences, which would be thought quite unimportant, are no
doubt sometimes of great service both to plants and animals. The Whitesmith's
gooseberry, as formerly stated, produces its leaves later than other
varieties, and, as the flowers are thus left unprotected, the fruit often
fails. In one variety of the cherry, according to Mr. Rivers (21/36.
'Gardener's Chronicle' 1866 page 732.), the petals are much curled backwards,
and in consequence of this the stigmas were observed to be killed by a severe
frost; whilst at the same time, in another variety with incurved petals, the
stigmas were not in the least injured. The straw of the Fenton wheat is
remarkably unequal in height; and a competent observer believes that this
variety is highly productive, partly because the ears from being distributed
at various heights above the ground are less crowded together. The same
observer maintains that in the upright varieties the divergent awns are
serviceable by breaking the shocks when the ears are dashed together by the
wind. (21/37. 'Gardener's Chronicle' 1862 pages 820, 821.) If several
varieties of a plant are grown together, and the seed is indiscriminately
harvested, it is clear that the hardier and more productive kinds will, by a
sort of natural selection, gradually prevail over the others; this takes
place, as Colonel Le Couteur believes (21/38. 'On the Varieties of Wheat' page
59.), in our wheat-fields, for, as formerly shown, no variety is quite uniform
in character. The same thing, as I am assured by nurserymen, would take place
in our flower-gardens, if the seed of the different varieties were not
separately saved. When the eggs of the wild and tame duck are hatched
together, the young wild ducks almost invariably perish, from being of smaller
size and not getting their fair share of food. (21/39. Mr. Hewitt and others,
in 'Journal of Hort.' 1862 page 773.)

Facts in sufficient number have now been given showing that natural selection
often checks, but occasionally favours, man's power of selection. These facts
teach us, in addition, a valuable lesson, namely, that we ought to be
extremely cautious in judging what characters are of importance in a state of
nature to animals and plants, which have to struggle for existence from the
hour of their birth to that of their death,--their existence depending on
conditions, about which we are profoundly ignorant.


The possibility of selection rests on variability, and this, as we shall see
in the following chapters, mainly depends on changed conditions of life, but
is governed by infinitely complex and unknown laws. Domestication, even when
long continued, occasionally causes but a small amount of variability, as in
the case of the goose and turkey. The slight differences, however, which
characterise each individual animal and plant would in most, probably in all,
cases suffice for the production of distinct races through careful and
prolonged selection. We see what selection, though acting on mere individual
differences, can effect when families of cattle, sheep, pigeons, etc., of the
same race, have been separately bred during a number of years by different men
without any wish on their part to modify the breed. We see the same fact in
the difference between hounds bred for hunting in different districts (21/40.
'Encyclop. of Rural Sports' page 405.), and in many other such cases.

In order that selection should produce any result, it is manifest that the
crossing of distinct races must be prevented; hence facility in pairing, as
with the pigeon, is highly favourable for the work; and difficulty in pairing,
as with cats, prevents the formation of distinct breeds. On nearly the same
principle the cattle of the small island of Jersey have been improved in their
milking qualities "with a rapidity that could not have been obtained in a
widely extended country like France." (21/41. Col. Le Couteur 'Journal Roy.
Agricult. Soc.' volume 4 page 43.) Although free crossing is a danger on the
one side which every one can see, too close interbreeding is a hidden danger
on the other side. Unfavourable conditions of life overrule the power of
selection. Our improved heavy breeds of cattle and sheep could not have been
formed on mountainous pastures; nor could dray-horses have been raised on a
barren and inhospitable land, such as the Falkland Islands, where even the
light horses of La Plata rapidly decrease in size. It seems impossible to
preserve several English breeds of sheep in France; for as soon as the lambs
are weaned their vigour decays as the heat of the summer increases (21/42.
Malingie-Nouel 'Journal R. Agricult. Soc.' volume 14 1853 pages 215, 217.): it
would be impossible to give great length of wool to sheep within the tropics;
yet selection has kept the Merino breed nearly true under diversified and
unfavourable conditions. The power of selection is so great, that breeds of
the dog, sheep, and poultry, of the largest and smallest size, long and short
beaked pigeons, and other breeds with opposite characters, have had their
characteristic qualities augmented, though treated in every way alike, being
exposed to the same climate and fed on the same food. Selection, however, is
either checked or favoured by the effects of use or habit. Our wonderfully-
improved pigs could never have been formed if they had been forced to search
for their own food; the English racehorse and greyhound could not have been
improved up to their present high standard of excellence without constant

As conspicuous deviations of structure occur rarely, the improvement of each
breed is generally the result of the selection of slight individual
differences. Hence the closest attention, the sharpest powers of observation,
and indomitable perseverance, are indispensable. It is, also, highly important
that many individuals of the breed which is to be improved should be raised;
for thus there will be a better chance of the appearance of variations in the
right direction, and individuals varying in an unfavourable manner may be
freely rejected or destroyed. But that a large number of individuals should be
raised, it is necessary that the conditions of life should favour the
propagation of the species. Had the peacock been reared as easily as the fowl,
we should probably ere this have had many distinct races. We see the
importance of a large number of plants, from the fact of nursery gardeners
almost always beating amateurs in the exhibition of new varieties. In 1845 it
was estimated (21/43. Gardener's Chronicle' 1845 page 273.) that between 4000
and 5000 pelargoniums were annually raised from seed in England, yet a
decidedly improved variety is rarely obtained. At Messrs. Carter's grounds, in
Essex, where such flowers as the Lobelia, Nemophila, Mignonette, etc., are
grown by the acre for seed, "scarcely a season passes without some new kinds
being raised, or some improvement effected on old kinds." (21/44. 'Journal of
Horticulture' 1862 page 157.) At Kew, as Mr. Beaton remarks, where many
seedlings of common plants are raised, "you see new forms of Laburnums,
Spiraeas, and other shrubs." (21/45. 'Cottage Gardener' 1860 page 368.) So
with animals: Marshall (21/46. 'A Review of Reports' 1808 page 406.), in
speaking of the sheep in one part of Yorkshire, remarks, "as they belong to
poor people, and are mostly in small lots, they never can be improved." Lord
Rivers, when asked how he succeeded in always having first-rate greyhounds,
answered, "I breed many, and hang many." This, as another man remarks, "was
the secret of his success; and the same will be found in exhibiting fowls,--
successful competitors breed largely, and keep the best." (21/47. 'Gardener's
Chronicle' 1853 page 45.)

It follows from this that the capacity of breeding at an early age and at
short intervals, as with pigeons, rabbits, etc., facilitates selection; for
the result is thus soon made visible, and perseverance in the work encouraged.
It can hardly be an accident that the great majority of the culinary and
agricultural plants which have yielded numerous races are annuals or
biennials, which therefore are capable of rapid propagation, and thus of
improvement. Sea-kale, asparagus, common and Jerusalem artichokes, potatoes,
and onions, must be excepted, as they are perennials: but onions are
propagated like annuals, and of the other plants just specified, none, with
the exception of the potato, have yielded in this country more than one or two
varieties. In the Mediterranean region, where artichokes are often raised from
seed, there are several kinds, as I hear from Mr. Bentham. No doubt fruit-
trees, which cannot be propagated quickly by seed, have yielded a host of
varieties, though not permanent races; but these, judging from prehistoric
remains, have been produced at a comparatively late period.

A species may be highly variable, but distinct races will not be formed, if
from any cause selection be not applied. It would be difficult to select
slight variations in fishes from their place of habitation; and though the
carp is extremely variable and is much attended to in Germany, only one well-
marked race has been formed, as I hear from Lord A. Russell, namely the
spiegel-carpe; and this is carefully secluded from the common scaly kind. On
the other hand, a closely allied species, the gold-fish, from being reared in
small vessels, and from having been carefully attended to by the Chinese, has
yielded many races. Neither the bee, which has been semi-domesticated from an
extremely remote period, nor the cochineal insect, which was cultivated by the
aboriginal Mexicans (21/48. Isidore Geoffroy Saint-Hilaire 'Hist. Nat. Gen.'
tome 3 page 49. 'On the Cochineal Insect' page 46.), has yielded races; and it
would be impossible to match the queen-bee with any particular drone, and most
difficult to match cochineal insects. Silk-moths, on the other hand, have been
subjected to rigorous selection, and have produced a host of races. Cats,
which from their nocturnal habits cannot be selected for breeding, do not, as
formerly remarked, yield distinct races within the same country. Dogs are held
in abomination in the East, and their breeding is neglected; consequently, as
Prof. Moritz Wagner (21/49. 'Die Darwin'sche Theorie und das Migrationsgesetz
der Organismen' 1868 page 19.) remarks, one kind alone exists there. The ass
in England varies much in colour and size; but as it is an animal of little
value and bred by poor people, there has been no selection, and distinct races
have not been formed. We must not attribute the inferiority of our asses to
climate, for in India they are of even smaller size than in Europe. But when
selection is brought to bear on the ass, all is changed. Near Cordova, as I am
informed (February 1860) by Mr. W.E. Webb, C.E., they are carefully bred, as
much as 200 pounds having been paid for a stallion ass, and they have been
immensely improved. In Kentucky, asses have been imported (for breeding mules)
from Spain, Malta, and France; these "seldom averaged more than fourteen hands
high: but the Kentuckians, by great care, have raised them up to fifteen
hands, and sometimes even to sixteen. The prices paid for these splendid
animals, for such they really are, will prove how much they are in request.
One male, of great celebrity, was sold for upwards of one thousand pounds
sterling." These choice asses are sent to cattle-shows, a day being given for
their exhibition. (21/50. Capt. Marryat quoted by Blyth in 'Journ. Asiatic
Soc. of Bengal' volume 28 page 229.)

Analogous facts have been observed with plants: the nutmeg-tree in the Malay
archipelago is highly variable, but there has been no selection, and there are
no distinct races. (21/51. Mr. Oxley 'Journal of the Indian Archipelago'
volume 2 1848 page 645.) The common mignonette (Reseda odorata), from bearing
inconspicuous flowers, valued solely for their fragrance, "remains in the same
unimproved condition as when first introduced." (21/52. Mr. Abbey 'Journal of
Horticulture' December 1, 1863 page 430.) Our common forest-trees are very
variable, as may be seen in every extensive nursery-ground; but as they are
not valued like fruit-trees, and as they seed late in life, no selection has
been applied to them; consequently, as Mr. Patrick Matthews remarks (21/53.
'On Naval Timber' 1831 page 107.), they have not yielded distinct races,
leafing at different periods, growing to different sizes, and producing timber
fit for different purposes. We have gained only some fanciful and semi-
monstrous varieties, which no doubt appeared suddenly as we now see them.

Some botanists have argued that plants cannot have so strong a tendency to
vary as is generally supposed, because many species long grown in botanic
gardens, or unintentionally cultivated year after year mingled with our corn
crops, have not produced distinct races; but this is accounted for by slight
variations not having been selected and propagated. Let a plant which is now
grown in a botanic garden, or any common weed, be cultivated on a large scale,
and let a sharp-sighted gardener look out for each slight variety and sow the
seed, and then, if distinct races are not produced, the argument will be

The importance of selection is likewise shown by considering special
characters. For instance, with most breeds of fowls the form of the comb and
the colour of the plumage have been attended to, and are eminently
characteristic of each race; but in Dorkings fashion has never demanded
uniformity of comb or colour; and the utmost diversity in these respects
prevails. Rose-combs, double-combs, cup-combs, etc., and colours of all kinds,
may be seen in purely bred and closely related Dorking fowls, whilst other
points, such as the general form of body, and the presence of an additional
toe, have been attended to, and are invariably present. It has also been
ascertained that colour can be fixed in this breed, as well as in any other.
(21/54. Mr. Baily in 'The Poultry Chronicle' volume 2 1854 page 150. Also
volume 1 page 342; volume 3 page 245.)

During the formation or improvement of a breed, its members will always be
found to vary much in those characters to which especial attention is
directed, and of which each slight improvement is eagerly sought and selected.
Thus, with short-faced tumbler-pigeons, the shortness of the beak, shape of
head and plumage,--with carriers, the length of the beak and wattle,--with
fantails, the tail and carriage,--with Spanish fowls, the white face and
comb,--with long-eared rabbits, the length of ear, are all points which are
eminently variable. So it is in every case; and the large price paid for
first-rate animals proves the difficulty of breeding them up to the highest
standard of excellence. This subject has been discussed by fanciers (21/55.
'Cottage Gardener' 1855 December page 171; 1856 January pages 248, 323.), and
the greater prizes given for highly improved breeds, in comparison with those
given for old breeds which are not now undergoing rapid improvement, have been
fully justified. Nathusius makes (21/56. 'Ueber Shorthorn Rindvieh' 1857 s.
51.) a similar remark when discussing the less uniform character of improved
Shorthorn cattle and of the English horse, in comparison, for example, with
the unennobled cattle of Hungary, or with the horses of the Asiatic steppes.
This want of uniformity in the parts which at the time are undergoing
selection chiefly depends on the strength of the principle of reversion; but
it likewise depends to a certain extent on the continued variability of the
parts which have recently varied. That the same parts do continue varying in
the same manner we must admit, for if it were not so, there could be no
improvement beyond an early standard of excellence, and we know that such
improvement is not only possible, but is of general occurrence.

As a consequence of continued variability, and more especially of reversion,
all highly improved races, if neglected or not subjected to incessant
selection, soon degenerate. Youatt gives a curious instance of this in some
cattle formerly kept in Glamorganshire; but in this case the cattle were not
fed with sufficient care. Mr. Baker, in his memoir on the Horse, sums up: "It
must have been observed in the preceding pages that, whenever there has been
neglect, the breed has proportionally deteriorated." (21/57. 'The Veterinary'
volume 13 page 720. For the Glamorganshire cattle see Youatt on 'Cattle' page
51.) If a considerable number of improved cattle, sheep, or other animals of
the same race, were allowed to breed freely together, with no selection, but
with no change in their condition of life, there can be no doubt that after a
score or hundred generations they would be very far from excellent of their
kind; but, from what we see of the many common races of dogs, cattle, fowls,
pigeons, etc., which without any particular care have long retained nearly the
same character, we have no grounds for believing that they would altogether
depart from their type.

It is a general belief amongst breeders that characters of all kinds become
fixed by long-continued inheritance. But I have attempted to show in the
fourteenth chapter that this belief apparently resolves itself into the
following proposition, namely, that all characters whatever, whether recently
acquired or ancient, tend to be transmitted, but that those which have already
long withstood all counteracting influences, will, as a general rule, continue
to withstand them, and consequently be faithfully transmitted.


It is an important principle that in the process of selection man almost
invariably wishes to go to an extreme point. Thus, there is no limit to his
desire to breed certain kinds of horses and dogs as fleet as possible, and
others as strong as possible; certain kinds of sheep for extreme fineness, and
others for extreme length of wool; and he wishes to produce fruit, grain,
tubers, and other useful parts of plants, as large and excellent as possible.
With animals bred for amusement, the same principle is even more powerful; for
fashion, as we see in our dress, always runs to extremes. This view has been
expressly admitted by fanciers. Instances were given in the chapters on the
pigeon, but here is another: Mr. Eaton, after describing a comparatively new
variety, namely, the Archangel, remarks, "What fanciers intend doing with this
bird I am at a loss to know, whether they intend to breed it down to the
tumbler's head and beak, or carry it out to the carrier's head and beak;
leaving it as they found it, is not progressing." Ferguson, speaking of fowls,
says, "their peculiarities, whatever they may be, must necessarily be fully
developed: a little peculiarity forms nought but ugliness, seeing it violates
the existing laws of symmetry." So Mr. Brent, in discussing the merits of the
sub-varieties of the Belgian canary-bird, remarks, "Fanciers always go to
extremes; they do not admire indefinite properties." (21/58. J.M. Eaton 'A
Treatise on Fancy Pigeons' page 82; Ferguson on 'Rare and Prize Poultry' page
162; Mr. Brent in 'Cottage Gardener' October 1860 page 13.)

This principle, which necessarily leads to divergence of character, explains
the present state of various domestic races. We can thus see how it is that
racehorses and dray-horses, greyhounds and mastiffs, which are opposed to each
other in every character,--how varieties so distinct as Cochin-china fowls and
bantams, or carrier-pigeons with very long beaks, and tumblers with
excessively short beaks, have been derived from the same stock. As each breed
is slowly improved, the inferior varieties are first neglected and finally
lost. In a few cases, by the aid of old records, or from intermediate
varieties still existing in countries where other fashions have prevailed, we
are enabled partially to trace the graduated changes through which certain
breeds have passed. Selection, whether methodical or unconscious, always
tending towards an extreme point, together with the neglect and slow
extinction of the intermediate and less-valued forms, is the key which unlocks
the mystery of how man has produced such wonderful results.

In a few instances selection, guided by utility for a single purpose, has led
to convergence of character. All the improved and different races of the pig,
as Nathusius has well shown (21/59. 'Die Racen des Schweines' 1860 s. 48.),
closely approach each other in character, in their shortened legs and muzzles,
their almost hairless, large, rounded bodies, and small tusks. We see some
degree of convergence in the similar outline of the body in well-bred cattle
belonging to distinct races. (21/60. See some good remarks on this head by M.
de Quatrefages 'Unite de l'Espece Humaine' 1861 page 119.) I know of no other
such cases.

Continued divergence of character depends on, and is indeed a clear proof, as
previously remarked, of the same parts continuing to vary in the same
direction. The tendency to mere general variability or plasticity of
organisation can certainly be inherited, even from one parent, as has been
shown by Gartner and Kolreuter, in the production of varying hybrids from two
species, of which one alone was variable. It is in itself probable that, when
an organ has varied in any manner, it will again vary in the same manner, if
the conditions which first caused the being to vary remain, as far as can be
judged, the same. This is either tacitly or expressly admitted by all
horticulturists: if a gardener observes one or two additional petals in a
flower, he feels confident that in a few generations he will be able to raise
a double flower, crowded with petals. Some of the seedlings from the weeping
Moccas oak were so prostrate that they only crawled along the ground. A
seedling from the fastigiate or upright Irish yew is described as differing
greatly from the parent-form "by the exaggeration of the fastigiate habit of
its branches." (21/61. Verlot 'Des Varietes' 1865 page 94.) Mr. Shirreff, who
has been highly successful in raising new kinds of wheat, remarks, "A good
variety may safely be regarded as the forerunner of a better one." (21/62. Mr.
Patrick Shirreff 'Gardener's Chronicle' 1858 page 771.) A great rose-grower,
Mr. Rivers, has made the same remark with respect to roses. Sageret (21/63.
'Pomologie Physiolog.' 1830 page 106.), who had large experience, in speaking
of the future progress of fruit-trees, observes that the most important
principle is "that the more plants have departed from their original type, the
more they tend to depart from it." There is apparently much truth in this
remark; for we can in no other way understand the surprising amount of
difference between varieties in the parts or qualities which are valued,
whilst other parts retain nearly their original character.

The foregoing discussion naturally leads to the question, what is the limit to
the possible amount of variation in any part or quality, and, consequently, is
there any limit to what selection can effect? Will a racehorse ever be reared
fleeter than Eclipse? Can our prize-cattle and sheep be still further
improved? Will a gooseberry ever weigh more than that produced by "London" in
1852? Will the beet-root in France yield a greater percentage of sugar? Will
future varieties of wheat and other grain produce heavier crops than our
present varieties? These questions cannot be positively answered; but it is
certain that we ought to be cautious in answering them by a negative. In some
lines of variation the limit has probably been reached. Youatt believes that
the reduction of bone in some of our sheep has already been carried so far
that it entails great delicacy of constitution. (21/64. Youatt on 'Sheep' page
521.) But seeing the great improvement within recent times in our cattle and
sheep, and especially in our pigs; seeing the wonderful increase in weight in
our poultry of all kinds during the last few years; he would be a bold man who
would assert that perfection has been reached. It has often been said that
Eclipse never was, and never will be, beaten in speed by any other horse; but
on making inquiries I find that the best judges believe that our present
racehorses are fleeter. (21/65. See also Stonehenge 'British Rural Sports'
edition of 1871 page 384.) The attempt to raise a new variety of wheat more
productive than the many old kinds, might have been thought until lately quite
hopeless; but this has been effected by Major Hallett, by careful selection.
With respect to almost all our animals and plants, those who are best
qualified to judge do not believe that the extreme point of perfection has yet
been reached even in the characters which have already been carried to a high
standard. For instance, the short-faced tumbler-pigeon has been greatly
modified; nevertheless, according to Mr. Eaton (21/66. 'A Treatise on the
Almond Tumbler' page 1.) "the field is still as open for fresh competitors as
it was one hundred years ago." Over and over again it has been said that
perfection had been attained with our flowers, but a higher standard has soon
been reached. Hardly any fruit has been more improved than the strawberry, yet
a great authority remarks (21/67. M. J. de Jonghe in 'Gardener's Chronicle'
1858 page 173.), "it must not be concealed that we are far from the extreme
limits at which we may arrive."

No doubt there is a limit beyond which the organisation cannot be modified
compatibly with health or life. The extreme degree of fleetness, for instance,
of which a terrestrial animal is capable, may have been acquired by our
present racehorses; but as Mr. Wallace has well remarked (21/68.
'Contributions to the Theory of Natural Selection' 2nd edition 1871 page
292.), the question that interests us, "is not whether indefinite and
unlimited change in any or all directions is possible, but whether such
differences as do occur in nature could have been produced by the accumulation
of varieties by selection." And in the case of our domestic productions, there
can be no doubt that many parts of the organisation, to which man has
attended, have been thus modified to a greater degree than the corresponding
parts in the natural species of the same genera or even families. We see this
in the form and size of our light and heavy dogs or horses,--in the beak and
many other characters of our pigeons,--in the size and quality of many
fruits,--in comparison with the species belonging to the same natural groups.

Time is an important element in the formation of our domestic races, as it
permits innumerable individuals to be born, and these when exposed to
diversified conditions are rendered variable. Methodical selection has been
occasionally practised from an ancient period to the present day, even by
semi-civilised people, and during former times will have produced some effect.
Unconscious selection will have been still more effective; for during a
lengthened period the more valuable individual animals will occasionally have
been saved, and the less valuable neglected. In the course of time, different
varieties, especially in the less civilised countries, will also have been
more or less modified through natural selection. It is generally believed,
though on this head we have little or no evidence, that new characters in time
become fixed; and after having long remained fixed it seems possible that
under new conditions they might again be rendered variable.

How great the lapse of time has been since man first domesticated animals and
cultivated plants, we begin dimly to see. When the lake-dwellings of
Switzerland were inhabited during the Neolithic period, several animals were
already domesticated and various plants cultivated. The science of language
tells us that the art of ploughing and sowing the land was followed, and the
chief animals had been already domesticated, at an epoch so immensely remote,
that the Sanskrit, Greek, Latin, Gothic, Celtic, and Sclavonic languages had
not as yet diverged from their common parent-tongue. (21/69. Max Muller
'Science of Language' 1861 page 223.)

It is scarcely possible to overrate the effects of selection occasionally
carried on in various ways and places during thousands of generations. All
that we know, and, in a still stronger degree, all that we do not know (21/70.
'Youatt on Cattle' pages 116, 128.), of the history of the great majority of
our breeds, even of our more modern breeds, agrees with the view that their
production, through the action of unconscious and methodical selection, has
been almost insensibly slow. When a man attends rather more closely than is
usual to the breeding of his animals, he is almost sure to improve them to a
slight extent. They are in consequence valued in his immediate neighbourhood,
and are bred by others; and their characteristic features, whatever these may
be, will then slowly but steadily be increased, sometimes by methodical and
almost always by unconscious selection. At last a strain, deserving to be
called a sub-variety, becomes a little more widely known, receives a local
name, and spreads. The spreading will have been extremely slow during ancient
and less civilised times, but now is rapid. By the time that the new breed had
assumed a somewhat distinct character, its history, hardly noticed at the
time, will have been completely forgotten; for, as Low remarks (21/71.
'Domesticated Animals' page 188.), "we know how quickly the memory of such
events is effaced."

As soon as a new breed is thus formed, it is liable through the same process
to break up into new strains and sub-varieties. For different varieties are
suited for, and are valued under, different circumstances. Fashion changes,
but, should a fashion last for even a moderate length of time, so strong is
the principle of inheritance, that some effect will probably be impressed on
the breed. Thus varieties go on increasing in number, and history shows us how
wonderfully they have increased since the earliest records. (21/72. Volz
'Beitrage zur Kulturgeschichte' 1852 s. 99 et passim.) As each new variety is
produced, the earlier, intermediate, and less valuable forms will be
neglected, and perish. When a breed, from not being valued, is kept in small
numbers, its extinction almost inevitably follows sooner or later, either from
accidental causes of destruction or from close interbreeding; and this is an
event which, in the case of well-marked breeds, excites attention. The birth
or production of a new domestic race is so slow a process that it escapes
notice; its death or destruction is comparatively sudden, is often recorded,
and when too late sometimes regretted.

Several authors have drawn a wide distinction between artificial and natural
races. The latter are more uniform in character, possessing in a high degree
the appearance of natural species, and are of ancient origin. They are
generally found in less civilised countries, and have probably been largely
modified by natural selection, and only to a small extent by man's unconscious
and methodical selection. They have, also, during a long period, been directly
acted on by the physical conditions of the countries which they inhabit. The
so-called artificial races, on the other hand, are not so uniform in
character; some have a semi-monstrous character, such as "the wry-legged
terriers so useful in rabbit-shooting" (21/73. Blaine 'Encyclop. of Rural
Sports' page 213.), turnspit dogs, ancon sheep, niata oxen, Polish fowls,
fantail-pigeons, etc.; their characteristic features have generally been
acquired suddenly, though subsequently increased by careful selections in many
cases. Other races, which certainly must be called artificial, for they have
been largely modified by methodical selection and by crossing, as the English
racehorse, terrier-dogs, the English game-cock, Antwerp carrier-pigeons, etc.,
nevertheless cannot be said to have an unnatural appearance; and no distinct
line, as it seems to me, can be drawn between natural and artificial races.

It is not surprising that domestic races should generally present a different
aspect from natural species. Man selects and propagates modifications solely
for his own use or fancy, and not for the creature's own good. His attention
is struck by strongly marked modifications, which have appeared suddenly, due
to some great disturbing cause in the organisation. He attends almost
exclusively to external characters; and when he succeeds in modifying internal
organs,--when for instance he reduces the bones and offal, or loads the
viscera with fat, or gives early maturity, etc.-the chances are strong that he
will at the same time weaken the constitution. On the other hand, when an
animal has to struggle throughout its life with many competitors and enemies,
under circumstances inconceivably complex and liable to change, modifications
of the most varied nature in the internal organs as well as in external
characters, in the functions and mutual relations of parts, will be rigorously
tested, preserved, or rejected. Natural selection often checks man's
comparatively feeble and capricious attempts at improvement; and if it were
not so, the result of his work, and of nature's work, would be even still more
different. Nevertheless, we must not overrate the amount of difference between
natural species and domestic races; the most experienced naturalists have
often disputed whether the latter are descended from one or from several
aboriginal stocks, and this clearly shows that there is no palpable difference
between species and races.

Domestic races propagate their kind far more truly, and endure for munch
longer periods, than most naturalists are willing to admit. Breeders feel no
doubt on this head: ask a man who has long reared Shorthorn or Hereford
cattle, Leicester or Southdown sheep, Spanish or Game poultry, tumbler or
carrier-pigeons, whether these races may not have been derived from common
progenitors, and he will probably laugh you to scorn. The breeder admits that
he may hope to produce sheep with finer or longer wool and with better
carcases, or handsomer fowls, or carrier-pigeons with beaks just perceptibly
longer to the practised eye, and thus be successful at an exhibition. Thus far
he will go, but no farther. He does not reflect on what follows from adding up
during a long course of time many slight, successive modifications; nor does
he reflect on the former existence of numerous varieties, connecting the links
in each divergent line of descent. He concludes, as was shown in the earlier
chapters, that all the chief breeds to which he has long attended are
aboriginal productions. The systematic naturalist, on the other hand, who
generally knows nothing of the art of breeding, who does not pretend to know
how and when the several domestic races were formed, who cannot have seen the
intermediate gradations, for they do not now exist, nevertheless feels no
doubt that these races are sprung from a single source. But ask him whether
the closely allied natural species which he has studied may not have descended
from a common progenitor, and he in his turn will perhaps reject the notion
with scorn. Thus the naturalist and breeder may mutually learn a useful lesson
from each other.


There can be no doubt that methodical selection has effected and will effect
wonderful results. It was occasionally practised in ancient times, and is
still practised by semi-civilised people. Characters of the highest
importance, and others of trifling value, have been attended to, and modified.
I need not here repeat what has been so often said on the part which
unconscious selection has played: we see its power in the difference between
flocks which have been separately bred, and in the slow changes, as
circumstances have slowly changed, which many animals have undergone in the
same country, or when transported into a foreign land. We see the combined
effects of methodical and unconscious selection, in the great amount of
difference in those parts or qualities which are valued by man in comparison
with the parts which are not valued, and consequently have not been attended
to. Natural selection often determines man's power of selection. We sometimes
err in imagining that characters, which are considered as unimportant by the
systematic naturalist, could not be affected by the struggle for existence,
and could not be acted on by natural selection; but striking cases have been
given, showing how great an error this is.

The possibility of selection coming into action rests on variability; and this
is mainly caused, as we shall hereafter see, by changes in the conditions of
life. Selection is sometimes rendered difficult, or even impossible, by the
conditions being opposed to the desired character or quality. It is sometimes
checked by the lessened fertility and weakened constitution which follow from
long-continued close interbreeding. That methodical selection may be
successful, the closest attention and discernment, combined with unwearied
patience, are absolutely necessary; and these same qualities, though not
indispensable, are highly serviceable in the case of unconscious selection. It
is almost necessary that a large number of individuals should be reared; for
thus there will be a fair chance of variations of the desired nature arising,
and of every individual with the slightest blemish or in any degree inferior
being freely rejected. Hence length of time is an important element of
success. Thus, also, reproduction at an early age and at short intervals
favours the work. Facility in pairing animals, or their inhabiting a confined
area, is advantageous as a check to free crossing. Whenever and wherever
selection is not practised, distinct races are not formed within the same
country. When any one part of the body or one quality is not attended to, it
remains either unchanged or varies in a fluctuating manner, whilst at the same
time other parts and other qualities may become permanently and greatly
modified. But from the tendency to reversion and to continued variability,
those parts or organs which are now undergoing rapid improvement through
selection, are likewise found to vary much. Consequently highly-bred animals
when neglected soon degenerate; but we have no reason to believe that the
effects of long-continued selection would, if the conditions of life remained
the same, be soon and completely lost.

Man always tends to go to an extreme point in the selection, whether
methodical or unconscious, of all useful and pleasing qualities. This is an
important principle, as it leads to continued divergence, and in some rare
cases to convergence of character. The possibility of continued divergence
rests on the tendency in each part or organ to go on varying in the same
manner in which it has already varied; and that this occurs, is proved by the
steady and gradual improvement of many animals and plants during lengthened
periods. The principle of divergence of character, combined with the neglect
and final extinction of all previous, less-valued, and intermediate varieties,
explains the amount of difference and the distinctness of our several races.
Although we may have reached the utmost limit to which certain characters can
be modified, yet we are far from having reached, as we have good reason to
believe, the limit in the majority of cases. Finally, from the difference
between selection as carried on by man and by nature, we can understand how it
is that domestic races often, though by no means always, differ in general
aspect from closely allied natural species.

Throughout this chapter and elsewhere I have spoken of selection as the
paramount power, yet its action absolutely depends on what we in our ignorance
call spontaneous or accidental variability. Let an architect be compelled to
build an edifice with uncut stones, fallen from a precipice. The shape of each
fragment may be called accidental; yet the shape of each has been determined
by the force of gravity, the nature of the rock, and the slope of the
precipice,--events and circumstances, all of which depend on natural laws; but
there is no relation between these laws and the purpose for which each
fragment is used by the builder. In the same manner the variations of each
creature are determined by fixed and immutable laws; but these bear no
relation to the living structure which is slowly built up through the power of
selection, whether this be natural or artificial selection.

If our architect succeeded in rearing a noble edifice, using the rough wedge-
shaped fragments for the arches, the longer stones for the lintels, and so
forth, we should admire his skill even in a higher degree than if he had used
stones shaped for the purpose. So it is with selection, whether applied by man
or by nature; for although variability is indispensably necessary, yet, when
we look at some highly complex and excellently adapted organism, variability
sinks to a quite subordinate position in importance in comparison with
selection, in the same manner as the shape of each fragment used by our
supposed architect is unimportant in comparison with his skill.




We will now consider, as far as we can, the causes of the almost universal
variability of our domesticated productions. The subject is an obscure one;
but it may be useful to probe our ignorance. Some authors, for instance Dr.
Prosper Lucas, look at variability as a necessary contingent on reproduction,
and as much an aboriginal law as growth or inheritance. Others have of late
encouraged, perhaps unintentionally, this view by speaking of inheritance and
variability as equal and antagonistic principles. Pallas maintained, and he
has had some followers, that variability depends exclusively on the crossing
of primordially distinct forms. Other authors attribute variability to an
excess of food, and with animals to an excess relatively to the amount of
exercise taken, or again to the effects of a more genial climate. That these
causes are all effective is highly probable. But we must, I think, take a
broader view, and conclude that organic beings, when subjected during several
generations to any change whatever in their conditions, tend to vary; the kind
of variation which ensues depending in most cases in a far higher degree on
the nature or constitution of the being, than on the nature of the changed

Those authors who believe that it is a law of nature that each individual
should differ in some slight degree from every other, may maintain, apparently
with truth, that this is the fact, not only with all domesticated animals and
cultivated plants, but likewise with all organic beings in a state of nature.
The Laplander by long practice knows and gives a name to each reindeer,
though, as Linnaeus remarks, "to distinguish one from another among such
multitudes was beyond my comprehension, for they were like ants on an
anthill." In Germany shepherds have won wagers by recognising each sheep in a
flock of a hundred, which they had never seen until the previous fortnight.
This power of discrimination, however, is as nothing compared to that which
some florists have acquired. Verlot mentions a gardener who could distinguish
150 kinds of camellia, when not in flower; and it has been positively asserted
that the famous old Dutch florist Voorhelm, who kept above 1200 varieties of
the hyacinth, was hardly ever deceived in knowing each variety by the bulb
alone. Hence we must conclude that the bulbs of the hyacinth and the branches
and leaves of the camellia, though appearing to an unpractised eye absolutely
undistinguishable, yet really differ. (22/1. 'Des Jacinthes' etc. Amsterdam
1768 page 43; Verlot 'Des Varietes' etc. page 86. On the reindeer see Linnaeus
'Tour in Lapland' translated by Sir J.E. Smith volume 1 page 314. The
statement in regard to German shepherds is given on the authority of Dr.

As Linnaeus has compared the reindeer in number to ants, I may add that each
ant knows its fellow of the same community. Several times I carried ants of
the same species (Formica rufa) from one ant-hill to another, inhabited
apparently by tens of thousands of ants; but the strangers were instantly
detected and killed. I then put some ants taken from a very large nest into a
bottle strongly perfumed with assafoetida, and after an interval of twenty-
four hours returned them to their home; they were at first threatened by their
fellows, but were soon recognised and allowed to pass. Hence each ant
certainly recognised, independently of odour, its fellow; and if all the ants
of the same community have not some countersign or watchword, they must
present to each other's senses some distinguishable character.

The dissimilarity of brothers or sisters of the same family, and of seedlings
from the same capsule, may be in part accounted for by the unequal blending of
the characters of the two parents, and by the more or less complete recovery
through reversion of ancestral characters on either side; but we thus only
push the difficulty further back in time, for what made the parents or their
progenitors different? Hence the belief (22/2. Muller 'Physiology' English
translation, volume 2 page 1662. With respect to the similarity of twins in
constitution, Dr. William Ogle has given me the following extract from
Professor Trousseau's Lectures 'Clinique Medicale' tome 1 page 523, in which a
curious case is recorded:--"J'ai donne mes soins a deux freres jumeaux, tous
deux si extraordinairement ressemblants qu'il m'etait impossible de les
reconnaitre, a moin de les voir l'un a cote de l'autre. Cette ressemblance
physique s'etendait plus loin: ils avaient, permettez-moi l'expression, une
similitude pathologique plus remarquable encore. Ainsi l'un d'eux que je
voyais aux neothermes a Paris malade d'une ophthalmie rhumatismale me disait,
'En ce moment mon frere doit avoir une ophthalmie comme la mienne;' et comme
je m'etais recrie, il me montrait quelques jours apres une lettre qu'il venait
de recevoir de ce frere alors a Vienne, et qui lui ecrivait en effet--'J'ai
mon ophthalmie, tu dois avoir la tienne.' Quelque singulier que ceci puisse
paraitre, le fait n'en est pas moins exact: on ne me l'a pas raconte, je l'ai
vu, et j'en ai vu d'autres analogues dans ma pratique. Ces deux jumeaux
etaient aussi tous deux asthmatiques, et asthmatiques a un effroyable degre.
Originaires de Marseille, ils n'ont jamais pu demeurer dans cette ville, ou
leurs interets les appelaient souvent, sans etre pris de leurs acces; jamais
ils n'en eprouvaient a Paris. Bien mieux, il leur suffisait de gagner Toulon
pour etre gueris de leurs attaques de Marseille. Voyageant sans cesse et dans
tous pays pour leurs affaires, ils avaient remarque que certaines localites
leur etaient funestes, que dans d'autres ils etaient exempts de tout phenomene
d'oppression.") that an innate tendency to vary exists, independently of
external differences, seems at first sight probable. But even the seeds
nurtured in the same capsule are not subjected to absolutely uniform
conditions, as they draw their nourishment from different points; and we shall
see in a future chapter that this difference sometimes suffices to affect the
character of the future plant. The greater dissimilarity of the successive
children of the same family in comparison with twins, which often resemble
each other in external appearance, mental disposition, and constitution, in so
extraordinary a manner, apparently proves that the state of the parents at the
exact period of conception, or the nature of the subsequent embryonic
development, has a direct and powerful influence on the character of the
offspring. Nevertheless, when we reflect on the individual differences between
organic beings in a state of nature, as shown by every wild animal knowing its
mate; and when we reflect on the infinite diversity of the many varieties of
our domesticated productions, we may well be inclined to exclaim, though
falsely as I believe, that Variability must be looked at as an ultimate fact,
necessarily contingent on reproduction.

Those authors who adopt this latter view would probably deny that each
separate variation has its own proper exciting cause. Although we can seldom
trace the precise relation between cause and effect, yet the considerations
presently to be given lead to the conclusion that each modification must have
its own distinct cause, and is not the result of what we blindly call
accident. The following striking case has been communicated to me by Dr.
William Ogle. Two girls, born as twins, and in all respects extremely alike,
had their little fingers on both hands crooked; and in both children the
second bicuspid tooth of the second dentition on the right side in the upper
jaw was misplaced; for, instead of standing in a line with the others, it grew
from the roof of the mouth behind the first bicuspid. Neither the parents nor
any other members of the family were known to have exhibited any similar
peculiarity; but a son of one of these girls had the same tooth similarly
misplaced. Now, as both the girls were affected in exactly the same manner,
the idea of accident is at once excluded: and we are compelled to admit that
there must have existed some precise and sufficient cause which, if it had
occurred a hundred times, would have given crooked fingers and misplaced
bicuspid teeth to a hundred children. It is of course possible that this case
may have been due to reversion to some long-forgotten progenitor, and this
would much weaken the value of the argument. I have been led to think of the
probability of reversion, from having been told by Mr. Galton of another case
of twin girls born with their little fingers slightly crooked, which they
inherited from their maternal grandmother.

We will now consider the general arguments, which appear to me to have great
weight, in favour of the view that variations of all kinds and degrees are
directly or indirectly caused by the conditions of life to which each being,
and more especially its ancestors, have been exposed.

No one doubts that domesticated productions are more variable than organic
beings which have never been removed from their natural conditions.
Monstrosities graduate so insensibly into mere variations that it is
impossible to separate them; and all those who have studied monstrosities
believe that they are far commoner with domesticated than with wild animals
and plants (22/3. Isid. Geoffroy St.-Hilaire 'Hist. des Anomalies' tome 3 page
352; Moquin-Tandon 'Teratologie Vegetale' 1841 page 115.); and in the case of
plants, monstrosities would be equally noticeable in the natural as in the
cultivated state. Under nature, the individuals of the same species are
exposed to nearly uniform conditions, for they are rigorously kept to their
proper places by a host of competing animals and plants; they have, also, long
been habituated to their conditions of life; but it cannot be said that they
are subject to quite uniform conditions, and they are liable to a certain
amount of variation. The circumstances under which our domestic productions
are reared are widely different: they are protected from competition; they
have not only been removed from their natural conditions and often from their
native land, but they are frequently carried from district to district, where
they are treated differently, so that they rarely remain during any
considerable length of time exposed to closely similar conditions. In
conformity with this, all our domesticated productions, with the rarest
exceptions, vary far more than natural species. The hive-bee, which feeds
itself and follows in most respects its natural habits of life, is the least
variable of all domesticated animals, and probably the goose is the next least
variable; but even the goose varies more than almost any wild bird, so that it
cannot be affiliated with perfect certainty to any natural species. Hardly a
single plant can be named, which has long been cultivated and propagated by
seed, that is not highly variable; common rye (Secale cereale) has afforded
fewer and less marked varieties than almost any other cultivated plant (22/4.
Metzger 'Die Getreidarten' 1841 s. 39.); but it may be doubted whether the
variations of this, the least valuable of all our cereals, have been closely

Bud-variation, which was fully discussed in a former chapter, shows us that
variability may be quite independent of seminal reproduction, and likewise of
reversion to long-lost ancestral characters. No one will maintain that the
sudden appearance of a moss-rose on a Provence-rose is a return to a former
state, for mossiness of the calyx has been observed in no natural species; the
same argument is applicable to variegated and laciniated leaves; nor can the
appearance of nectarines on peach-trees be accounted for on the principle of
reversion. But bud-variations more immediately concern us, as they occur far
more frequently on plants which have been highly cultivated during a length of
time, than on other and less highly cultivated plants; and very few well-
marked instances have been observed with plants growing under strictly natural
conditions. I have given one instance of an ash-tree growing in a gentleman's
pleasure-grounds; and occasionally there may be seen, on beech and other
trees, twigs leafing at a different period from the other branches. But our
forest trees in England can hardly be considered as living under strictly
natural conditions; the seedlings are raised and protected in nursery-grounds,
and must often be transplanted into places where wild trees of the kind would
not naturally grow. It would be esteemed a prodigy if a dog-rose growing in a
hedge produced by bud-variation a moss-rose, or a wild bullace or wild cherry-
tree yielded a branch bearing fruit of a different shape and colour from the
ordinary fruit. The prodigy would be enhanced if these varying branches were
found capable of propagation, not only by grafts, but sometimes by seed; yet
analogous cases have occurred with many of our highly cultivated trees and

These several considerations alone render it probable that variability of
every kind is directly or indirectly caused by changed conditions of life. Or,
to put the case under another point of view, if it were possible to expose all
the individuals of a species during many generations to absolutely uniform
conditions of life, there would be no variability.


From a remote period to the present day, under climates and circumstances as
different as it is possible to conceive, organic beings of all kinds, when
domesticated or cultivated, have varied. We see this with the many domestic
races of quadrupeds and birds belonging to different orders, with goldfish and
silkworms, with plants of many kinds, raised in various quarters of the world.
In the deserts of northern Africa the date-palm has yielded thirty-eight
varieties; in the fertile plains of India it is notorious how many varieties
of rice and of a host of other plants exist; in a single Polynesian island,
twenty-four varieties of the bread-fruit, the same number of the banana, and
twenty-two varieties of the arum, are cultivated by the natives; the mulberry-
tree in India and Europe has yielded many varieties serving as food for the
silkworm; and in China sixty-three varieties of the bamboo are used for
various domestic purposes. (22/5. On the date-palm see Vogel 'Annals and Mag.
of Nat. Hist.' 1854 page 460. On Indian varieties Dr. F. Hamilton 'Transact.
Linn. Soc.' volume 14 page 296. On the varieties cultivated in Tahiti see Dr.
Bennett in Loudon's 'Mag. of N. Hist.' volume 5 1832 page 484. Also Ellis
'Polynesian Researches' volume 1 pages 370, 375. On twenty varieties of the
Pandanus and other trees in the Marianne Island see 'Hooker's Miscellany'
volume 1 page 308. On the bamboo in China see Huc 'Chinese Empire' volume 2
page 307.) These facts, and innumerable others which could be added, indicate
that a change of almost any kind in the conditions of life suffices to cause
variability--different changes acting on different organisms.

Andrew Knight (22/6. 'Treatise on the Culture of the Apple' etc. page 3.)
attributed the variation of both animals and plants to a more abundant supply
of nourishment, or to a more favourable climate, than that natural to the
species. A more genial climate, however, is far from necessary; the kidney-
bean, which is often injured by our spring frosts, and peaches, which require
the protection of a wall, have varied much in England, as has the orange-tree
in northern Italy, where it is barely able to exist. (22/7. Gallesio 'Teoria
della Riproduzione Veg.' page 125.) Nor can we overlook the fact, though not
immediately connected with our present subject, that the plants and shells of
the Arctic regions are eminently variable. (22/8. See Dr. Hooker's Memoir on
Arctic Plants in 'Linn. Transact.' volume 23 part 2. Mr. Woodward, and a
higher authority cannot be quoted, speaks of the Arctic mollusca in his
'Rudimentary Treatise' 1856 page 355 as remarkably subject to variation.)
Moreover, it does not appear that a change of climate, whether more or less
genial, is one of the most potent causes of variability; for in regard to
plants Alph. De Candolle, in his 'Geographie Botanique' repeatedly shows that
the native country of a plant, where in most cases it has been longest
cultivated, is that where it has yielded the greatest number of varieties.

It is doubtful whether a change in the nature of the food is a potent cause of
variability. Scarcely any domesticated animal has varied more than the pigeon
or the fowl, but their food, especially that of highly-bred pigeons, is
generally the same. Nor can our cattle and sheep have been subjected to any
great change in this respect. But in all these cases the food probably is much
less varied in kind than that which was consumed by the species in its natural
state. (22/9. Bechstein in his 'Naturgeschichte der Stubenvogel' 1840 s. 238,
has some good remarks on this subject. He states that his canary-birds varied
in colour, though kept on uniform food.)

Of all the causes which induce variability, excess of food, whether or not
changed in nature, is probably the most powerful. This view was held with
regard to plants by Andrew Knight, and is now held by Schleiden, more
especially in reference to the inorganic elements of the food. (22/10. 'The
Plant' by Schleiden translated by Henfrey 1848 page 169. See also Alex. Braun
in 'Bot. Memoirs' Ray Soc. 1853 page 313.) In order to give a plant more food
it suffices in most cases to grow it separately, and thus prevent other plants
robbing its roots. It is surprising, as I have often seen, how vigorously our
common wild species flourish when planted by themselves, though not in highly
manured land; separate growth is, in fact, the first step in cultivation. We
see the converse of the belief that excess of food induces variability in the
following statement by a great raiser of seeds of all kinds (22/11. Messrs.
Hardy and Son of Maldon in 'Gardener's Chronicle' 1856 page 458. Carriere
'Production et Fixation des Varietes' 1865 page 31.): "It is a rule invariably
with us, when we desire to keep a true stock of any one kind of seed, to grow
it on poor land without dung; but when we grow for quantity, we act contrary,
and sometimes have dearly to repent of it." According also to Carriere, who
has had great experience with flower-garden seeds, "On remarque en general les
plantes de vigeur moyenne sont celles qui conservent le mieux leurs

In the case of animals the want of a proper amount of exercise, as Bechstein
remarked, has perhaps played, independently of the direct effects of the
disuse of any particular organ, an important part in causing variability. We
can see in a vague manner that, when the organised and nutrient fluids of the
body are not used during growth, or by the wear and tear of the tissues, they
will be in excess; and as growth, nutrition, and reproduction are intimately
allied processes, this superfluity might disturb the due and proper action of
the reproductive organs, and consequently affect the character of the future
offspring. But it may be argued that neither an excess of food nor a
superfluity in the organised fluids of the body necessarily induces
variability. The goose and the turkey have been well fed for many generations,
yet have varied very little. Our fruit-trees and culinary plants, which are so
variable, have been cultivated from an ancient period, and, though they
probably still receive more nutriment than in their natural state, yet they
must have received during many generations nearly the same amount; and it
might be thought that they would have become habituated to the excess.
Nevertheless, on the whole, Knight's view, that excess of food is one of the
most potent causes of variability, appears, as far as I can judge, probable.

Whether or not our various cultivated plants have received nutriment in
excess, all have been exposed to changes of various kinds. Fruit-trees are
grafted on different stocks, and grown in various soils. The seeds of culinary
and agricultural plants are carried from place to place; and during the last
century the rotation of our crops and the manures used have been greatly

Slight changes of treatment often suffice to induce variability. The simple
fact of almost all our cultivated plants and domesticated animals having
varied in all places and at all times, leads to this conclusion. Seeds taken
from common English forest-trees, grown under their native climate, not highly
manured or otherwise artificially treated, yield seedlings which vary much, as
may be seen in every extensive seed-bed. I have shown in a former chapter what
a number of well-marked and singular varieties the thorn (Crataegus oxycantha)
has produced: yet this tree has been subjected to hardly any cultivation. In
Staffordshire I carefully examined a large number of two British plants,
namely Geranium phaeum and pyrenaicum, which have never been highly
cultivated. These plants had spread spontaneously by seed from a common garden
into an open plantation; and the seedlings varied in almost every single
character, both in their flower and foliage, to a degree which I have never
seen exceeded; yet they could not have been exposed to any great change in
their conditions.

With respect to animals, Azara has remarked with much surprise (22/12.
'Quadrupedes du Paraguay' 1801 tome 2 page 319.) that, whilst the feral horses
on the Pampas are always of one of three colours, and the cattle always of a
uniform colour, yet these animals, when bred on the unenclosed estancias,
though kept in a state which can hardly be called domesticated, and apparently
exposed to almost identically the same conditions as when they are feral,
nevertheless display a great diversity of colour. So again in India several
species of fresh-water fish are only so far treated artificially, that they
are reared in great tanks; but this small change is sufficient to induce much
variability. (22/13. M'Clelland on Indian Cyprinidae 'Asiatic Researches'
volume 19 part 2 1839 pages 266, 268, 313.)

Some facts on the effects of grafting, in regard to the variability of trees,
deserve attention. Cabanis asserts that when certain pears are grafted on the
quince, their seeds yield a greater number of varieties than do the seeds of
the same variety of pear when grafted on the wild pear. (22/14. Quoted by
Sageret 'Pom. Phys.' 1830 page 43. This statement, however, is not believed by
Decaisne.) But as the pear and quince are distinct species, though so closely
related that the one can be readily grafted and succeeds admirably on the
other, the fact of variability being thus caused is not surprising; as we are
here enabled to see the cause, namely, the very different nature of the stock
and graft. Several North American varieties of the plum and peach are well
known to reproduce themselves truly by seed; but Downing asserts (22/15. 'The
Fruits of America' 1845 page 5.), "that when a graft is taken from one of
these trees and placed upon another stock, this grafted tree is found to lose
its singular property of producing the same variety by seed, and becomes like
all other worked trees;"--that is, its seedlings become highly variable.
Another case is worth giving: the Lalande variety of the walnut-tree leafs
between April 20th and May 15th, and its seedlings invariably inherit the same
habit; whilst several other varieties of the walnut leaf in June. Now, if
seedlings are raised from the May-leafing Lalande variety, grafted on another
May-leafing variety, though both stock and graft have the same early habit of
leafing, yet the seedlings leaf at various times, even as late as the 5th of
June. (22/16. M. Cardan in 'Comptes Rendus' December 1848 quoted in
'Gardener's Chronicle' 1849 page 101.) Such facts as these are well fitted to
show on what obscure and slight causes variability depends.

[I may here just allude to the appearance of new and valuable varieties of
fruit-trees and of wheat in woods and waste places, which at first sight seems
a most anomalous circumstance. In France a considerable number of the best
pears have been discovered in woods; and this has occurred so frequently, that
Poiteau asserts that "improved varieties of our cultivated fruits rarely
originate with nurserymen." (22/17. M. Alexis Jordan mentions four excellent
pears found in woods in France, and alludes to others ('Mem. Acad. de Lyon'
tome 2 1852 page 159). Poiteau's remark is quoted in 'Gardener's Mag.' volume
4 1828 page 385. See 'Gardener's Chronicle' 1862 page 335, for another case of
a new variety of the pear found in a hedge in France. Also for another case,
see Loudon's 'Encyclop. of Gardening' page 901. Mr. Rivers has given me
similar information.) In England, on the other hand, no instance of a good
pear having been found wild has been recorded; and Mr. Rivers informs me that
he knows of only one instance with apples, namely, the Bess Poole, which was
discovered in a wood in Nottinghamshire. This difference between the two
countries may be in part accounted for by the more favourable climate of
France, but chiefly from the great number of seedlings which spring up there
in the woods. I infer that this is the case from a remark made by a French
gardener (22/18. Duval 'Hist. du Poirier' 1849 page 2.), who regards it as a
national calamity that such a number of pear-trees are periodically cut down
for firewood, before they have borne fruit. The new varieties which thus
spring up in the woods, though they cannot have received any excess of
nutriment, will have been exposed to abruptly changed conditions, but whether
this is the cause of their production is very doubtful. These varieties,
however, are probably all descended (22/19. I infer that this is the fact from
Van Mons' statement ('Arbres Fruitiers' 1835 tome 1 page 446) that he finds
in the woods seedlings resembling all the chief cultivated races of both the
pear and apple. Van Mons, however, looked at these wild varieties as
aboriginal species.) from old cultivated kinds growing in adjoining orchards--
a circumstance which will account for their variability; and out of a vast
number of varying trees there will always be a good chance of the appearance
of a valuable kind. In North America, where fruit-trees frequently spring up
in waste places, the Washington pear was found in a hedge, and the Emperor
peach in a wood. (22/20. Downing 'Fruit-trees of North America' page 422;
Foley in 'Transact. Hort. Soc.' volume 6 page 412.)

With respect to wheat, some writers have spoken (22/21. 'Gardener's Chronicle'
1847 page 244.) as if it were an ordinary event for new varieties to be found
in waste places; the Fenton wheat was certainly discovered growing on a pile
of basaltic detritus in a quarry, but in such a situation the plant would
probably receive a sufficient amount of nutriment. The Chidham wheat was
raised from an ear found ON a hedge; and Hunter's wheat was discovered BY the
roadside in Scotland, but it is not said that this latter variety grew where
it was found. (22/22. 'Gardener's Chronicle' 1841 page 383; 1850 page 700;
1854 page 650.)]

Whether our domestic productions would ever become so completely habituated to
the conditions under which they now live, as to cease varying, we have no
sufficient means for judging. But, in fact, our domestic productions are never
exposed for a great length of time to uniform conditions, and it is certain
that our most anciently cultivated plants, as well as animals, still go on
varying, for all have recently undergone marked improvement. In some few
cases, however, plants have become habituated to new conditions. Thus,
Metzger, who cultivated in Germany during many years numerous varieties of
wheat, brought from different countries (22/23. 'Die Getreidearten' 1843 s.
66, 116, 117.), states that some kinds were at first extremely variable, but
gradually, in one instance after an interval of twenty-five years, became
constant; and it does not appear that this resulted from the selection of the
more constant forms.


We have good grounds for believing that the influence of changed conditions
accumulates, so that no effect is produced on a species until it has been
exposed during several generations to continued cultivation or domestication.
Universal experience shows us that when new flowers are first introduced into
our gardens they do not vary; but ultimately all, with the rarest exceptions,
vary to a greater or less extent. In a few cases the requisite number of
generations, as well as the successive steps in the progress of variation,
have been recorded, as in the often quoted instance of the Dahlia. (22/24.
Sabine in 'Hort. Transact.' volume 3 page 225; Bronn 'Geschichte der Natur' b.
2 s. 119.) After several years' culture the Zinnia has only lately (1860)
begun to vary in any great degree. "In the first seven or eight years of high
cultivation, the Swan River daisy (Brachycome iberidifolia) kept to its
original colour; it then varied into lilac and purple and other minor shades."
(22/25. 'Journal of Horticulture' 1861 page 112; on Zinnia 'Gardener's
Chronicle' 1860 page 852.) Analogous facts have been recorded with the Scotch
rose. In discussing the variability of plants several experienced
horticulturists have spoken to the same general effect. Mr. Salter (22/26.
'The Chrysanthemum, its History, etc.' 1865 page 3.) remarks, "Every one knows
that the chief difficulty is in breaking through the original form and colour
of the species, and every one will be on the look-out for any natural sport,
either from seed or branch; that being once obtained, however trifling the
change may be, the result depends upon himself." M. de Jonghe, who has had so
much success in raising new varieties of pears and strawberries (22/27.
'Gardener's Chronicle' 1855 page 54; 'Journal of Horticulture' May 9, 1865
page 363.), remarks with respect to the former, "There is another principle,
namely, that the more a type has entered into a state of variation, the
greater is its tendency to continue doing so; and the more it has varied from
the original type, the more it is disposed to vary still farther." We have,
indeed, already discussed this latter point when treating of the power which
man possesses, through selection, of continually augmenting in the same
direction each modification; for this power depends on continued variability
of the same general kind. The most celebrated horticulturist in France,
namely, Vilmorin (22/28. Quoted by Verlot 'Des Varietes' etc. 1865 page 28.),
even maintains that, when any particular variation is desired, the first step
is to get the plant to vary in any manner whatever, and to go on selecting the
most variable individuals, even though they vary in the wrong direction; for
the fixed character of the species being once broken, the desired variation
will sooner or later appear.

As nearly all our animals were domesticated at an extremely remote epoch, we
cannot, of course, say whether they varied quickly or slowly when first
subjected to new conditions. But Dr. Bachman (22/29. 'Examination of the
Characteristics of Genera and Species' Charleston 1855 page 14.) states that
he has seen turkeys raised from the eggs of the wild species lose their
metallic tints and become spotted with white in the third generation. Mr.
Yarrell many years ago informed me that the wild ducks bred on the ponds in
St. James's Park, which had never been crossed, as it is believed, with
domestic ducks, lost their true plumage after a few generations. An excellent
observer (22/30. Mr. Hewitt 'Journal of Hort.' 1863 page 39.), who has often
reared ducks from the eggs of the wild bird, and who took precautions that
there should be no crossing with domestic breeds, has given, as previously
stated, full details on the changes which they gradually undergo. He found
that he could not breed these wild ducks true for more than five or six
generations, "as they then proved so much less beautiful. The white collar
round the neck of the mallard became much broader and more irregular, and
white feathers appeared in the ducklings' wings." They increased also in size
of body; their legs became less fine, and they lost their elegant carriage.
Fresh eggs were then procured from wild birds; but again the same result
followed. In these cases of the duck and turkey we see that animals, like
plants, do not depart from their primitive type until they have been subjected
during several generations to domestication. On the other hand, Mr. Yarrell
informed me that the Australian dingos, bred in the Zoological Gardens, almost
invariably produced in the first generation puppies marked with white and
other colours; but, these introduced dingos had probably been procured from
the natives, who keep them in a semi-domesticated state. It is certainly a
remarkable fact that changed conditions should at first produce, as far as we
can see, absolutely no effect; but that they should subsequently cause the
character of the species to change. In the chapter on pangenesis I shall
attempt to throw a little light on this fact.

Returning now to the causes which are supposed to induce variability. Some
authors (22/31. Devay 'Mariages Consanguins' pages 97, 125. In conversation I
have found two or three naturalists of the same opinion.) believe that close
interbreeding gives this tendency, and leads to the production of
monstrosities. In the seventeenth chapter some few facts were advanced,
showing that monstrosities are, as it appears, occasionally thus induced; and
there can be no doubt that close interbreeding causes lessened fertility and a
weakened constitution; hence it may lead to variability: but I have not
sufficient evidence on this head. On the other hand, close interbreeding, if
not carried to an injurious extreme, far from causing variability, tends to
fix the character of each breed.

It was formerly a common belief, still held by some persons, that the
imagination of the mother affects the child in the womb. (22/32. Muller has
conclusively argued against this belief, 'Elements of Phys.' English
translation volume 2 1842 page 1405.) This view is evidently not applicable to
the lower animals, which lay unimpregnated eggs, or to plants. Dr. William
Hunter, in the last century, told my father that during many years every woman
in a large London Lying-in Hospital was asked before her confinement whether
anything had specially affected her mind, and the answer was written down; and
it so happened that in no one instance could a coincidence be detected between
the woman's answer and any abnormal structure; but when she knew the nature of
the structure, she frequently suggested some fresh cause. The belief in the
power of the mother's imagination may perhaps have arisen from the children of
a second marriage resembling the previous father, as certainly sometimes
occurs, in accordance with the facts given in the eleventh chapter.


In an early part of this chapter it was stated that Pallas (22/33. 'Act. Acad.
St. Petersburg' 1780 part 2 page 84 etc.) and a few other naturalists maintain
that variability is wholly due to crossing. If this means that new characters
never spontaneously appear in our domestic races, but that they are all
directly derived from certain aboriginal species, the doctrine is little less
than absurd; for it implies that animals like Italian greyhounds, pug-dogs,
bull-dogs, pouter and fantail pigeons, etc., were able to exist in a state of
nature. But the doctrine may mean something widely different, namely, that the
crossing of distinct species is the sole cause of the first appearance of new
characters, and that without this aid man could not have formed his various
breeds. As, however, new characters have appeared in certain cases by bud-
variation, we may conclude with certainty that crossing is not necessary for
variability. It is, moreover, certain that the breeds of various animals, such
as of the rabbit, pigeon, duck, etc., and the varieties of several plants, are
the modified descendants of a single wild species. Nevertheless, it is
probable that the crossing of two forms, when one or both have long been
domesticated or cultivated, adds to the variability of the offspring,
independently of the commingling of the characters derived from the two
parent-forms; and this implies that new characters actually arise. But we must
not forget the facts advanced in the thirteenth chapter, which clearly prove
that the act of crossing often leads to the reappearance or reversion of long-
lost characters; and in most cases it would be impossible to distinguish
between the reappearance of ancient characters and the first appearance of
absolutely new characters. Practically, whether new or old, they would be new
to the breed in which they reappeared.

[Gartner declares (22/34. 'Bastarderzeugung' s. 249, 255, 295.), and his
experience is of the highest value on such a point, that, when he crossed
native plants which had not been cultivated, he never once saw in the
offspring any new character; but that from the odd manner in which the
characters derived from the parents were combined, they sometimes appeared as
if new. When, on the other hand, he crossed cultivated plants, he admits that
new characters occasionally appeared, but he is strongly inclined to attribute
their appearance to ordinary variability, not in any way to the cross. An
opposite conclusion, however, appears to me the more probable. According to
Kolreuter, hybrids in the genus Mirabilis vary almost infinitely, and he
describes new and singular characters in the form of the seeds, in the colour
of the anthers, in the cotyledons being of immense size, in new and highly
peculiar odours, in the flowers expanding early in the season, and in their
closing at night. With respect to one lot of these hybrids, he remarks that
they presented characters exactly the reverse of what might have been expected
from their parentage. (22/35. 'Nova Acta, St. Petersburg' 1794 page 378; 1795
pages 307, 313, 316; 1787 page 407.)

Prof. Lecoq (22/36. 'De la Fecondation' 1862 page 311.) speaks strongly to the
same effect in regard to this same genus, and asserts that many of the hybrids
from Mirabilis jalapa and multiflora might easily be mistaken for distinct
species, and adds that they differed in a greater degree than the other
species of the genus, from M. jalapa. Herbert, also, has described (22/37.
'Amaryllidaceae' 1837 page 362.) certain hybrid Rhododendrons as being "as
UNLIKE ALL OTHERS in foliage, as if they had been a separate species." The
common experience of floriculturists proves that the crossing and recrossing
of distinct but allied plants, such as the species of Petunia, Calceolaria,
Fuchsia, Verbena, etc., induces excessive variability; hence the appearance of
quite new characters is probable. M. Carriere (22/38. Abstracted in
'Gardener's Chronicle' 1860 page 1081.) has lately discussed this subject: he
states that Erythrina cristagalli had been multiplied by seed for many years,
but had not yielded any varieties: it was then crossed with the allied E.
herbacea, and "the resistance was now overcome, and varieties were produced
with flowers of extremely different size, form, and colour."

From the general and apparently well-founded belief that the crossing of
distinct species, besides commingling their characters, adds greatly to their
variability, it has probably arisen that some botanists have gone so far as to
maintain (22/39. This was the opinion of the elder De Candolle, as quoted in
'Dic. Class. d'Hist. Nat.' tome 8 page 405. Puvis in his work 'De la
Degeneration' 1837 page 37, has discussed this same point.) that, when a genus
includes only a single species, this when cultivated never varies. The
proposition made so broadly cannot be admitted; but it is probably true that
the variability of monotypic genera when cultivated is generally less than
that of genera including numerous species, and this quite independently of the
effects of crossing. I have shown in my 'Origin of Species' that the species
belonging to small genera generally yield a less number of varieties in a
state of nature than those belonging to large genera. Hence the species of
small genera would, it is probable, produce fewer varieties under cultivation
than the already variable species of larger genera.

Although we have not at present sufficient evidence that the crossing of
species, which have never been cultivated, leads to the appearance of new
characters, this apparently does occur with species which have been already
rendered in some degree variable through cultivation. Hence crossing, like any
other change in the conditions of life, seems to be an element, probably a
potent one, in causing variability. But we seldom have the means of
distinguishing, as previously remarked, between the appearance of really new
characters and the reappearance of long-lost characters, evoked through the
act of crossing. I will give an instance of the difficulty in distinguishing
such cases. The species of Datura may be divided into two sections, those
having white flowers with green stems, and those having purple flowers with
brown stems: now Naudin (22/40. 'Comptes Rendus' Novembre 21, 1864 page 838.)
crossed Datura laevis and ferox, both of which belong to the white section,
and raised from them 205 hybrids. Of these hybrids, every one had brown stems
and bore purple flowers; so that they resembled the species of the other
section of the genus, and not their own two parents. Naudin was so much
astonished at this fact, that he was led carefully to observe both parent-
species, and he discovered that the pure seedlings of D. ferox, immediately
after germination, had dark purple stems, extending from the young roots up to
the cotyledons, and that this tint remained ever afterwards as a ring round
the base of the stem of the plant when old. Now I have shown in the thirteenth
chapter that the retention or exaggeration of an early character is so
intimately related to reversion, that it evidently comes under the same
principle. Hence probably we ought to look at the purple flowers and brown
stems of these hybrids, not as new characters due to variability, but as a
return to the former state of some ancient progenitor.

Independently of the appearance of new characters from crossing, a few words
may be added to what has been said in former chapters on the unequal
combination and transmission of the characters proper to the two parent-forms.
When two species or races are crossed, the offspring of the first generation
are generally uniform, but those subsequently produced display an almost
infinite diversity of character. He who wishes, says Kolreuter (22/41. 'Nova
Acta, St. Petersburg' 1794 page 391.), to obtain an endless number of
varieties from hybrids should cross and recross them. There is also much
variability when hybrids or mongrels are reduced or absorbed by repeated
crosses with either pure parent-form: and a still higher degree of variability
when three distinct species, and most of all when four species, are blended
together by successive crosses. Beyond this point Gartner (22/42.
'Bastarderzeugung' s. 507, 516, 572.), on whose authority the foregoing
statements are made, never succeeded in effecting a union; but Max Wichura
(22/43. 'Die Bastardbefruchtung' etc. 1865 s. 24.) united six distinct species
of willows into a single hybrid. The sex of the parent species affects in an
inexplicable manner the degree of variability of hybrids; for Gartner (22/44.
'Bastarderzeugung' s. 452, 507.) repeatedly found that when a hybrid was used
as a father and either one of the pure parent-species, or a third species, was
used as the mother, the offspring were more variable than when the same hybrid
was used as the mother, and either pure parent or the same third species as
the father: thus seedlings from Dianthus barbatus crossed by the hybrid D.
chinensi-barbatus were more variable than those raised from this latter hybrid
fertilised by the pure D. barbatus. Max Wichura (22/45. 'Die
Bastardbefruchtung' s. 56.) insists strongly on an analogous result with his
hybrid willows. Again Gartner (22/46. 'Bastarderzeugung' s. 423.) asserts that
the degree of variability sometimes differs in hybrids raised from reciprocal
crosses between the same two species; and here the sole difference is, that
the one species is first used as the father and then as the mother. On the
whole we see that, independently of the appearance of new characters, the
variability of successive crossed generations is extremely complex, partly
from the offspring partaking unequally of the characters of the two parent-
forms, and more especially from their unequal tendency to revert to such
characters or to those of more ancient progenitors.]


This is an extremely obscure subject, and we need here only consider, whether
inherited variations are due to certain parts being acted on after they have
been formed, or through the reproductive system being affected before their
formation; and in the former case at what period of growth or development the
effect is produced. We shall see in the two following chapters that various
agencies, such as an abundant supply of food, exposure to a different climate,
increased use or disuse of parts, etc., prolonged during several generations,
certainly modify either the whole organisation or certain organs; and it is
clear at least in the case of bud-variation that the action cannot have been
through the reproductive system.

[With respect to the part which the reproductive system takes in causing
variability, we have seen in the eighteenth chapter that even slight changes
in the conditions of life have a remarkable power in causing a greater or less
degree of sterility. Hence it seems not improbable that beings generated
through a system so easily affected should themselves be affected, or should
fail to inherit, or inherit in excess, characters proper to their parents. We
know that certain groups of organic beings, but with exceptions in each group,
have their reproductive systems much more easily affected by changed
conditions than other groups; for instance, carnivorous birds, more readily
than carnivorous mammals, and parrots more readily than pigeons; and this fact
harmonises with the apparently capricious manner and degree in which various
groups of animals and plants vary under domestication.

Kolreuter (22/47. 'Dritte Fortsetzung' etc. 1766 s. 85.) was struck with the
parallelism between the excessive variability of hybrids when crossed and
recrossed in various ways,--these hybrids having their reproductive powers
more or less affected,--and the variability of anciently cultivated plants.
Max Wichura (22/48. 'Die Bastardbefruchtung' etc. 1865 s. 92: see also the
Rev. M.J. Berkeley on the same subject in 'Journal of Royal Hort. Soc.' 1866
page 80.) has gone one step farther, and shows that with many of our highly
cultivated plants, such as the hyacinth, tulip, auricula, snapdragon, potato,
cabbage, etc., which there is no reason to believe have been hybridised, the
anthers contain many irregular pollen-grains in the same state as in hybrids.
He finds also in certain wild forms, the same coincidence between the state of
the pollen and a high degree of variability, as in many species of Rubus; but
in R. caesius and idaeus, which are not highly variable species, the pollen is
sound. It is also notorious that many cultivated plants, such as the banana,
pineapple, bread-fruit, and others previously mentioned, have their
reproductive organs so seriously affected as to be generally quite sterile;
and when they do yield seed, the seedlings, judging from the large number of
cultivated races which exist, must be variable in an extreme degree. These
facts indicate that there is some relation between the state of the
reproductive organs and a tendency to variability; but we must not conclude
that the relation is strict. Although many of our highly cultivated plants may
have their pollen in a deteriorated condition, yet, as we have previously
seen, they yield more seeds, and our anciently domesticated animals are more
prolific, than the corresponding species in a state of nature. The peacock is
almost the only bird which is believed to be less fertile under domestication
than in its native state, and it has varied in a remarkably small degree. From
these considerations it would seem that changes in the conditions of life lead
either to sterility or to variability, or to both; and not that sterility
induces variability. On the whole it is probable that any cause affecting the
organs of reproduction would likewise affect their product,--that is, the
offspring thus generated.

The period of life at which the causes that induce variability act, is
likewise an obscure subject, which has been discussed by various authors.
(22/49. Dr. P. Lucas has given a history of opinion on this subject 'Hered.
Nat.' 1847 tome 1 page 175.) In some of the cases, to be given in the
following chapter, of modifications from the direct action of changed
conditions, which are inherited, there can be no doubt that the causes have
acted on the mature or nearly mature animal. On the other hand, monstrosities,
which cannot be distinctly separated from lesser variations, are often caused
by the embryo being injured whilst in the mother's womb or in the egg. Thus I.
Geoffroy Saint-Hilaire (22/50. 'Hist. des Anomalies' tome 3 page 499.) asserts
that poor women who work hard during their pregnancy, and the mothers of
illegitimate children troubled in their minds and forced to conceal their
state, are far more liable to give birth to monsters than women in easy
circumstances. The eggs of the fowl when placed upright or otherwise treated
unnaturally frequently produce monstrous chickens. It would, however, appear
that complex monstrosities are induced more frequently during a rather late
than during a very early period of embryonic life; but this may partly result
from some one part, which has been injured during an early period, affecting
by its abnormal growth other parts subsequently developed; and this would be
less likely to occur with parts injured at a later period. (22/51. Ibid tome 3
pages 392, 502. The several memoirs by M. Dareste hereafter referred to are of
special value on this whole subject.) When any part or organ becomes monstrous
through abortion, a rudiment is generally left, and this likewise indicates
that its development had already commenced.

Insects sometimes have their antennae or legs in a monstrous condition, the
larvae of which do not possess either antennae or legs; and in these cases, as
Quatrefages (22/52. See his interesting work 'Metamorphoses de l'Homme' etc.
1862 page 129.) believes, we are enabled to see the precise period at which
the normal progress of development was troubled. But the nature of the food
given to a caterpillar sometimes affects the colours of the moth, without the
caterpillar itself being affected; therefore it seems possible that other
characters in the mature insect might be indirectly modified through the
larvae. There is no reason to suppose that organs which have been rendered
monstrous have always been acted on during their development; the cause may
have acted on the organisation at a much earlier stage. It is even probable
that either the male or female sexual elements, or both, before their union,
may be affected in such a manner as to lead to modifications in organs
developed at a late period of life; in nearly the same manner as a child may
inherit from his father a disease which does not appear until old age.

In accordance with the facts above given, which prove that in many cases a
close relation exists between variability and the sterility following from
changed conditions, we may conclude that the exciting cause often acts at the
earliest possible period, namely, on the sexual elements, before impregnation
has taken place. That an affection of the female sexual element may induce
variability we may likewise infer as probable from the occurrence of bud-
variations; for a bud seems to be the analogue of an ovule. But the male
element is apparently much oftener affected by changed conditions, at least in
a visible manner, than the female element or ovule and we know from Gartner's
and Wichura's statements that a hybrid used as the father and crossed with a
pure species gives a greater degree of variability to the offspring, than does
the same hybrid when used as the mother. Lastly, it is certain that
variability may be transmitted through either sexual element, whether or not
originally excited in them, for Kolreuter and Gartner (22/53. 'Dritte
Fortsetzung' etc. s. 123; 'Bastarderzeugung' s. 249.) found that when two
species were crossed, if either one was variable, the offspring were rendered


From the facts given in this chapter, we may conclude that the variability of
organic beings under domestication, although so general, is not an inevitable
contingent on life, but results from the conditions to which the parents have
been exposed. Changes of any kind in the conditions of life, even extremely
slight changes, often suffice to cause variability. Excess of nutriment is
perhaps the most efficient single exciting cause. Animals and plants continue
to be variable for an immense period after their first domestication; but the
conditions to which they are exposed never long remain quite constant. In the
course of time they can be habituated to certain changes, so as to become less
variable; and it is possible that when first domesticated they may have been
even more variable than at present. There is good evidence that the power of
changed conditions accumulates; so that two, three, or more generations must
be exposed to new conditions before any effect is visible. The crossing of
distinct forms, which have already become variable, increases in the offspring
the tendency to further variability, by the unequal commingling of the
characters of the two parents, by the reappearance of long-lost characters,
and by the appearance of absolutely new characters. Some variations are
induced by the direct action of the surrounding conditions on the whole
organisation, or on certain parts alone; other variations appear to be induced
indirectly through the reproductive system being affected, as we know is often
the case with various beings, which when removed from their natural conditions
become sterile. The causes which induce variability act on the mature
organism, on the embryo, and, probably, on the sexual elements before
impregnation has been effected.




If we ask ourselves why this or that character has been modified under
domestication, we are, in most cases, lost in utter darkness. Many
naturalists, especially of the French school, attribute every modification to
the "monde ambiant," that is, to changed climate, with all its diversities of
heat and cold, dampness and dryness, light and electricity, to the nature of
the soil, and to varied kinds and amount of food. By the term definite action,
as used in this chapter, I mean an action of such a nature that, when many
individuals of the same variety are exposed during several generations to any
particular change in their conditions of life, all, or nearly all the
individuals, are modified in the same manner. The effects of habit, or of the
increased use and disuse of various organs, might have been included under
this head; but it will be convenient to discuss this subject in a separate
chapter. By the term indefinite action I mean an action which causes one
individual to vary in one way and another individual in another way, as we
often see with plants and animals after they have been subjected for some
generations to changed conditions of life. But we know far too little of the
causes and laws of variation to make a sound classification. The action of
changed conditions, whether leading to definite or indefinite results, is a
totally distinct consideration from the effects of selection; for selection
depends on the preservation by man of certain individuals, or on their
survival under various and complex natural circumstances, and has no relation
whatever to the primary cause of each particular variation.

I will first give in detail all the facts which I have been able to collect,
rendering it probable that climate, food, etc., have acted so definitely and
powerfully on the organisation of our domesticated productions, that new sub-
varieties or races have been thus formed without the aid of selection by man
or nature. I will then give the facts and considerations opposed to this
conclusion, and finally we will weigh, as fairly as we can, the evidence on
both sides.

When we reflect that distinct races of almost all our domesticated animals
exist in each kingdom of Europe, and formerly even in each district of
England, we are at first strongly inclined to attribute their origin to the
definite action of the physical conditions of each country; and this has been
the conclusion of many authors. But we should bear in mind that man annually
has to choose which animals shall be preserved for breeding, and which shall
be slaughtered. We have also seen that both methodical and unconscious
selection were formerly practised, and are now occasionally practised by the
most barbarous races, to a much greater extent than might have been
anticipated. Hence it is difficult to judge how far differences in the
conditions between, for instance, the several districts in England, have
sufficed to modify the breeds which have been reared in each. It may be argued
that, as numerous wild animals and plants have ranged during many ages
throughout Great Britain, and still retain the same character, the difference
in conditions between the several districts could not have modified in a
marked manner the various native races of cattle, sheep, pigs, and horses. The
same difficulty of distinguishing between the effects of natural selection and
the definite action of external conditions is encountered in a still higher
degree when we compare closely allied species inhabiting two countries, such
as North America and Europe, which do not differ greatly in climate, nature of
soil, etc., for in this case natural selection will inevitably and rigorously
have acted during a long succession of ages.

Prof. Weismann has suggested (23/1. 'Ueber den Einfluss der Isolirung auf die
Artbildung' 1872.) that when a variable species enters a new and isolated
country, although the variations may be of the same general nature as before,
yet it is improbable that they should occur in the same proportional numbers.
After a longer or shorter period, the species will tend to become nearly
uniform in character from the incessant crossing of the varying individuals;
but owing to the proportion of the individuals varying in different ways not
being the same in the two cases, the final result will be the production of
two forms somewhat different from one another. In cases of this kind it would
falsely appear as if the conditions had induced certain definite
modifications, whereas they had only excited indefinite variability, but with
the variations in slightly different proportional numbers. This view may throw
some light on the fact that the domestic animals which formerly inhabited the
several districts in Great Britain, and the half wild cattle lately kept in
several British parks, differed slightly from one another; for these animals
were prevented from wandering over the whole country and intercrossing, but
would have crossed freely within each district or park.

[From the difficulty of judging how far changed conditions have caused
definite modifications of structure, it will be advisable to give as large a
body of facts as possible, showing that extremely slight differences within
the same country, or during different seasons, certainly produce an
appreciable effect, at least on varieties which are already in an unstable
condition. Ornamental flowers are good for this purpose, as they are highly
variable, and are carefully observed. All floriculturists are unanimous that
certain varieties are affected by very slight differences in the nature of the
artificial compost in which they are grown, and by the natural soil of the
district, as well as by the season. Thus, a skilful judge, in writing on
Carnations and Picotees (23/2. 'Gardener's Chronicle' 1853 page 183.) asks
"where can Admiral Curzon be seen possessing the colour, size, and strength
which it has in Derbyshire? Where can Flora's Garland be found equal to those
at Slough? Where do high-coloured flowers revel better than at Woolwich and
Birmingham? Yet in no two of these districts do the same varieties attain an
equal degree of excellence, although each may be receiving the attention of
the most skilful cultivators." The same writer then recommends every
cultivator to keep five different kinds of soil and manure, "and to endeavour
to suit the respective appetites of the plants you are dealing with, for
without such attention all hope of general success will be vain." So it is
with the Dahlia (23/3. Mr. Wildman 'Floricultural Soc.' February 7, 1843
reported in 'Gardener's Chronicle' 1843 page 86.): the Lady Cooper rarely
succeeds near London, but does admirably in other districts; the reverse holds
good with other varieties; and again, there are others which succeed equally
well in various situations. A skilful gardener (23/4. Mr. Robson in 'Journal
of Horticulture' February 13, 1866 page 122.) states that he procured cuttings
of an old and well-known variety (pulchella) of Verbena, which from having
been propagated in a different situation presented a slightly different shade
of colour; the two varieties were afterwards multiplied by cuttings, being
carefully kept distinct; but in the second year they could hardly be
distinguished, and in the third year no one could distinguish them.

The nature of the season has an especial influence on certain varieties of the
Dahlia: in 1841 two varieties were pre-eminently good, and the next year these
same two were pre-eminently bad. A famous amateur (23/5. 'Journal of
Horticulture' 1861 page 24.) asserts that in 1861 many varieties of the Rose
came so untrue in character, "that it was hardly possible to recognise them,
and the thought was not seldom entertained that the grower had lost his
tally." The same amateur (23/6. Ibid 1862 page 83.) states that in 1862 two-
thirds of his Auriculas produced central trusses of flowers, and such trusses
are liable not to keep true; and he adds that in some seasons certain
varieties of this plant all prove good, and the next season all prove bad;
whilst exactly the reverse happens with other varieties. In 1845 the editor of
the 'Gardener's Chronicle' (23/7. 'Gardener's Chronicle' 1845 page 660.)
remarked how singular it was that this year many Calceolarias tended to assume
a tubular form. With Heartsease (23/8. Ibid 1863 page 628.) the blotched sorts
do not acquire their proper character until hot weather sets in; whilst other
varieties lose their beautiful marks as soon as this occurs.

Analogous facts have been observed with leaves: Mr. Beaton asserts (23/9.
'Journal of Hort.' 1861 pages 64, 309.) that he raised at Shrubland, during
six years, twenty thousand seedlings from the Punch Pelargonium, and not one
had variegated leaves; but at Surbiton, in Surrey, one-third, or even a
greater proportion, of the seedlings from this same variety were more or less
variegated. The soil of another district in Surrey has a strong tendency to
cause variegation, as appears from information given me by Sir F. Pollock.
Verlot (23/10. 'Des Varietes' etc. page 76.) states that the variegated
strawberry retains its character as long as grown in a dryish soil, but soon
loses it when planted in fresh and humid soil. Mr. Salter, who is well known
for his success in cultivating variegated plants, informs me that rows of
strawberries were planted in his garden in 1859, in the usual way; and at
various distances in one row, several plants simultaneously became variegated;
and what made the case more extraordinary, all were variegated in precisely
the same manner. These plants were removed, but during the three succeeding
years other plants in the same row became variegated, and in no instance were
the plants in any adjoining row affected.

The chemical qualities, odours, and tissues of plants are often modified by a
change which seems to us slight. The Hemlock is said not to yield conicine in
Scotland. The root of the Aconitum napellus becomes innocuous in frigid
climates. The medicinal properties of the Digitalis are easily affected by
culture. As the Pistacia lentiscus grows abundantly in the South of France,
the climate must suit it, but it yields no mastic. The Laurus sassafras in
Europe loses the odour proper to it in North America. (23/11. Engel 'Sur les
Prop. Medicales des Plantes' 1860 pages 10, 25. On changes in the odours of
plants see Dalibert's Experiments quoted by Beckman 'Inventions' volume 2 page
344; and Nees in Ferussac 'Bull. des Sc. Nat.' 1824 tome 1 page 60. With
respect to the rhubarb etc. see also 'Gardener's Chronicle' 1849 page 355;
1862 page 1123.) Many similar facts could be given, and they are remarkable
because it might have been thought that definite chemical compounds would have
been little liable to change either in quality or quantity.

The wood of the American Locust-tree (Robinia) when grown in England is nearly
worthless, as is that of the Oak-tree when grown at the Cape of Good Hope.
(23/12. Hooker 'Flora Indica' page 32.) Hemp and flax, as I hear from Dr.
Falconer, flourish and yield plenty of seed on the plains of India, but their
fibres are brittle and useless. Hemp, on the other hand, fails to produce in
England that resinous matter which is so largely used in India as an
intoxicating drug.

The fruit of the Melon is greatly influenced by slight differences in culture
and climate. Hence it is generally a better plan, according to Naudin, to
improve an old kind than to introduce a new one into any locality. The seed of
the Persian Melon produces near Paris fruit inferior to the poorest market
kinds, but at Bordeaux yields delicious fruit. (23/13. Naudin 'Annales des Sc.
Nat.' 4th series, Bot. tome 11 1859 page 81. 'Gardener's Chronicle' 1859 page
464.) Seed is annually brought from Thibet to Kashmir (23/14. Moorcroft
'Travels' etc. volume 2 page 143.) and produces fruit weighing from four to
ten pounds, but plants raised next year from seed saved in Kashmir give fruit
weighing only from two to three pounds. It is well known that American
varieties of the Apple produce in their native land magnificent and brightly-
coloured fruit, but these in England are of poor quality and a dull colour. In
Hungary there are many varieties of the kidney-bean, remarkable for the beauty
of their seeds, but the Rev. M.J. Berkeley (23/15. 'Gardener's Chronicle' 1861
page 1113.) found that their beauty could hardly ever be preserved in England,
and in some cases the colour was greatly changed. We have seen in the ninth
chapter, with respect to wheat, what a remarkable effect transportal from the
north to the south of France, and conversely, produced on the weight of the

When man can perceive no change in plants or animals which have been exposed
to a new climate or to different treatment, insects can sometimes perceive a
marked change. A cactus has been imported into India from Canton, Manilla
Mauritius, and from the hot-houses of Kew, and there is likewise a so-called
native kind which was formerly introduced from South America; all these plants
belong to the same species and are alike in appearance, but the cochineal
insect flourishes only on the native kind, on which it thrives prodigiously.
(23/16. Royle 'Productive Resources of India' page 59.) Humboldt remarks
(23/17. 'Personal Narrative' English translation volume 5 page 101. This
statement has been confirmed by Karsten 'Beitrag zur Kenntniss der
Rhynchoprion' Moscow 1864 s. 39 and by others.) that white men "born in the
torrid zone walk barefoot with impunity in the same apartment where a
European, recently landed, is exposed to the attacks of the Pulex penetrans."
This insect, the too well-known chigoe, must therefore be able to perceive
what the most delicate chemical analysis fails to discover, namely, a
difference between the blood or tissues of a European and those of a white man
born in the tropics. But the discernment of the chigoe is not so surprising as
it at first appears; for according to Liebig (23/18. 'Organic Chemistry'
English translation 1st edition page 369.) the blood of men with different
complexions, though inhabiting the same country, emits a different odour.

[Diseases peculiar to certain localities, heights, or climates, may be here
briefly noticed, as showing the influence of external circumstances on the
human body. Diseases confined to certain races of man do not concern us, for
the constitution of the race may play the more important part, and this may
have been determined by unknown causes. The Plica Polonica stands, in this
respect, in a nearly intermediate position; for it rarely affects Germans, who
inhabit the neighbourhood of the Vistula, where so many Poles are grievously
affected; neither does it affect Russians, who are said to belong to the same
original stock as the Poles. (23/19. Prichard 'Phys. Hist. of Mankind' 1851
volume 1 page 155.) The elevation of a district often governs the appearance
of diseases; in Mexico the yellow fever does not extend above 924 metres; and
in Peru, people are affected with the verugas only between 600 and 1600 metres
above the sea; many other such cases could be given. A peculiar cutaneous
complaint, called the Bouton d'Alep, affects in Aleppo and some neighbouring
districts almost every native infant, and some few strangers; and it seems
fairly well established that this singular complaint depends on drinking
certain waters. In the healthy little island of St. Helena the scarlet-fever
is dreaded like the Plague; analogous facts have been observed in Chili and
Mexico. (23/20. Darwin 'Journal of Researches' 1845 page 434.) Even in the
different departments of France it is found that the various infirmities which
render the conscript unfit for serving in the army, prevail with remarkable
inequality, revealing, as Boudin observes, that many of them are endemic,
which otherwise would never have been suspected. (23/21. These statements on
disease are taken from Dr. Boudin 'Geographie et Statistique Medicale' 1857
tome 1 pages 44 and 52; tome 2 page 315.) Any one who will study the
distribution of disease will be struck with surprise at what slight
differences in the surrounding circumstances govern the nature and severity of
the complaints by which man is at least temporarily affected.

The modifications as yet referred to are extremely slight, and in most cases
have been caused, as far as we can judge, by equally slight differences in the
conditions. But such conditions acting during a series of generations would
perhaps produce a marked effect.

With plants, a considerable change of climate sometimes produces a conspicuous
result. I have given in the ninth chapter the most remarkable case known to
me, namely, that of varieties of maize, which were greatly modified in the
course of only two or three generations when taken from a tropical country to
a cooler one, or conversely. Dr. Falconer informs me that he has seen the
English Ribston-pippin apple, a Himalayan oak, Prunus and Pyrus, all assume in
the hotter parts of India a fastigiate or pyramidal habit; and this fact is
the more interesting, as a Chinese tropical species of Pyrus naturally grows
thus. Although in these cases the changed manner of growth seems to have been
directly caused by the great heat, we know that many fastigiate trees have
originated in their temperate homes. In the Botanic Gardens of Ceylon the
apple-tree (23/22. 'Ceylon' by Sir J.E. Tennent volume 1 1859 page 89.) "sends
out numerous runners under ground, which continually rise into small stems,
and form a growth around the parent-tree.) The varieties of the cabbage which
produce heads in Europe fail to do so in certain tropical countries (23/23.
Godron 'De l'Espece' tome 2 page 52.) The Rhododendron ciliatum produced at
Kew flowers so much larger and paler-coloured than those which it bears on its
native Himalayan mountain, that Dr. Hooker (23/24. 'Journal of Horticultural
Soc.' volume 7 1852 page 117.) would hardly have recognised the species by the
flowers alone. Many similar facts with respect to the colour and size of
flowers could be given.

The experiments of Vilmorin and Buckman on carrots and parsnips prove that
abundant nutriment produces a definite and inheritable effect on the roots,
with scarcely any change in other parts of the plant. Alum directly influences
the colour of the flowers of the Hydrangea. (23/25. 'Journal of Hort. Soc.'
volume 1 page 160.) Dryness seems generally to favour the hairiness or
villosity of plants. Gartner found that hybrid Verbascums became extremely
woolly when grown in pots. Mr. Masters, on the other hand, states that the
Opuntia leucotricha "is well clothed with beautiful white hairs when grown in
a damp heat, but in a dry heat exhibits none of this peculiarity." (23/26. See
Lecoq on the Villosity of Plants 'Geograph. Bot.' tome 3 pages 287, 291;
Gartner 'Bastarderz.' s. 261; Mr. Masters on the Opuntia in 'Gardener's
Chronicle' 1846 page 444.) Slight variations of many kinds, not worth
specifying in detail, are retained only as long as plants are grown in certain
soils, of which Sageret (23/27. 'Pom. Phys.' page 136.) gives some instances
from his own experience. Odart, who insists strongly on the permanence of the
varieties of the grape, admits (23/28. 'Ampelographie' 1849 page 19.) that
some varieties, when grown under a different climate or treated differently,
vary in a slight degree, as in the tint of the fruit and in the period of
ripening. Some authors have denied that grafting causes even the slightest
difference in the scion; but there is sufficient evidence that the fruit is
sometimes slightly affected in size and flavour, the leaves in duration, and
the flowers in appearance. (23/29. Gartner 'Bastarderz.' s. 606, has collected
nearly all recorded facts. Andrew Knight in 'Transact. Hort. Soc.' volume 2
page 160, goes so far as to maintain that few varieties are absolutely
permanent in character when propagated by buds or grafts.)

There can be no doubt, from the facts given in the first chapter, that
European dogs deteriorate in India, not only in their instincts but in
structure; but the changes which they undergo are of such a nature, that they
may be partly due to reversion to a primitive form, as in the case of feral
animals. In parts of India the turkey becomes reduced in size, "with the
pendulous appendage over the beak enormously developed." (23/30. Mr. Blyth
'Annals and Mag of Nat. Hist.' volume 20 1847 page 391.) We have seen how soon
the wild duck, when domesticated, loses its true character, from the effects
of abundant or changed food, or from taking little exercise. From the direct
action of a humid climate and poor pasture the horse rapidly decreases in size
in the Falkland Islands. From information which I have received, this seems
likewise to be the case to a certain extent with sheep in Australia.

Climate definitely influences the hairy covering of animals; in the West
Indies a great change is produced in the fleece of sheep, in about three
generations. Dr. Falconer states (23/31. 'Natural History Review' 1862 page
113.) that the Thibet mastiff and goat, when brought down from the Himalaya to
Kashmir, lose their fine wool. At Angora not only goats, but shepherd-dogs and
cats, have fine fleecy hair, and Mr. Ainsworth (23/32. 'Journal of Roy.
Geographical Soc.' volume 9 1839 page 275.) attributes the thickness of the
fleece to the severe winters, and its silky lustre to the hot summers. Burnes
states positively (23/33. 'Travels in Bokhara' volume 3 page 151.) that the
Karakool sheep lose their peculiar black curled fleeces when removed into any
other country. Even within the limits of England, I have been assured that the
wool of two breeds of sheep was slightly changed by the flocks being pastured
in different localities. (23/34. See also on the influence of marshy pastures
on the wool Godron 'L'Espece' tome 2 page 22.) It has been asserted on good
authority (23/35. Isidore Geoffroy Saint-Hilaire 'Hist. Nat. Gen.' tome 3 page
438.) that horses kept during several years in the deep coal-mines of Belgium
become covered with velvety hair, almost like that on the mole. These cases
probably stand in close relation to the natural change of coat in winter and
summer. Naked varieties of several domestic animals have occasionally
appeared; but there is no reason to believe that this is in any way related to
the nature of the climate to which they have been exposed. (23/36. Azara has
made some good remarks on this subject 'Quadrupedes du Paraguay' tome 2 page
337. See an account of a family of naked mice produced in England 'Proc.
Zoolog. Soc.' 1856 page 38.)

It appears at first sight probable that the increased size, the tendency to
fatten, the early maturity and altered forms of our improved cattle, sheep,
and pigs, have directly resulted from their abundant supply of food. This is
the opinion of many competent judges, and probably is to a great extent true.
But as far as form is concerned, we must not overlook the more potent
influence of lessened use on the limbs and lungs. We see, moreover, as far as
size is concerned, that selection is apparently a more powerful agent than a
large supply of food, for we can thus only account for the existence, as
remarked to me by Mr. Blyth, of the largest and smallest breeds of sheep in
the same country, of Cochin-China fowls and Bantams, of small Tumbler and
large Runt pigeons, all kept together and supplied with abundant nourishment.
Nevertheless there can be little doubt that our domesticated animals have been
modified, independently of the increased or lessened use of parts, by the
conditions to which they have been subjected, without the aid of selection.
For instance, Prof. Rutimeyer (23/37. 'Die Fauna der Pfahlbauten' 1861 s. 15.)
shows that the bones of domesticated quadrupeds can be distinguished from
those of wild animals by the state of their surface and general appearance. It
is scarcely possible to read Nathusius's excellent 'Vorstudien' (23/38.
'Schweineschadel' 1864 s. 99.) and doubt that, with the highly improved races
of the pig, abundant food has produced a conspicuous effect on the general
form of the body, on the breadth of the head and face, and even on the teeth.
Nathusius rests much on the case of a purely bred Berkshire pig, which when
two months old became diseased in its digestive organs, and was preserved for
observation until nineteen months old; at this age it had lost several
characteristic features of the breed, and had acquired a long, narrow head, of
large size relatively to its small body, and elongated legs. But in this case
and in some others we ought not to assume that, because certain characters are
lost, perhaps through reversion, under one course of treatment, therefore that
they were at first directly produced by an opposite treatment.

In the case of the rabbit, which has become feral on the island of Porto
Santo, we are at first strongly tempted to attribute the whole change--the
greatly reduced size, the altered tints of the fur, and the loss of certain
characteristic marks--to the definite action of the new conditions to which it
has been exposed. But in all such cases we have to consider in addition the
tendency to reversion to progenitors more or less remote, and the natural
selection of the finest shades of difference.

The nature of the food sometimes either definitely induces certain
peculiarities, or stands in some close relation with them. Pallas long ago
asserted that the fat-tailed sheep of Siberia degenerate and lose their
enormous tails when removed from certain saline pastures; and recently Erman
(23/39. 'Travels in Siberia' English translation volume 1 page 228.) states
that this occurs with the Kirgisian sheep when brought to Orenburgh.

It is well known that hemp-seed causes bullfinches and certain other birds to
become black. Mr. Wallace has communicated to me some much more remarkable
facts of the same nature. The natives of the Amazonian region feed the common
green parrot (Chrysotis festiva, Linn.) with the fat of large Siluroid fishes,
and the birds thus treated become beautifully variegated with red and yellow
feathers. In the Malayan archipelago, the natives of Gilolo alter in an
analogous manner the colours of another parrot, namely, the Lorius garrulus,
Linn., and thus produce the Lori rajah or King-Lory. These parrots in the
Malay Islands and South America, when fed by the natives on natural vegetable
food, such as rice and plaintains, retain their proper colours. Mr. Wallace
has, also, recorded (23/40. A.R. Wallace 'Travels on the Amazon and Rio Negro'
page 294.) a still more singular fact. "The Indians (of S. America) have a
curious art by which they change the colours of the feathers of many birds.
They pluck out those from the part they wish to paint, and inoculate the fresh
wound with the milky secretion from the skin of a small toad. The feathers
grow of a brilliant yellow colour, and on being plucked out, it is said, grow
again of the same colour without any fresh operation."

Bechstein (23/41. 'Naturgeschichte der Stubenvogel' 1840 s. 262, 308.) does
not entertain any doubt that seclusion from light affects, at least
temporarily, the colours of cage-birds.

It is well known that the shells of land-mollusca are affected by the
abundance of lime in different districts. Isidore Geoffroy Saint-Hilaire
(23/42. 'Hist. Nat Gen.' tome 3 page 402.) gives the case of Helix lactea,
which has recently been carried from Spain to the South of France and to the
Rio Plata, and in both countries now presents a distinct appearance, but
whether this has resulted from food or climate is not known. With respect to
the common oyster, Mr. F. Buckland informs me that he can generally
distinguish the shells from different districts; young oysters brought from
Wales and laid down in beds where "natives" are indigenous, in the short space
of two months begin to assume the "native" character. M. Costa (23/43. 'Bull.
de La Soc. Imp. d'Acclimat.' tome 8 page 351.) has recorded a much more
remarkable case of the same nature, namely, that young shells taken from the
shores of England and placed in the Mediterranean, at once altered their
manner of growth and formed prominent diverging rays, like those on the shells
of the proper Mediterranean oyster. The same individual shell, showing both
forms of growth, was exhibited before a society in Paris. Lastly, it is well
known that caterpillars fed on different food sometimes either themselves
acquire a different colour or produce moths differing in colour. (23/44. See
an account of Mr. Gregson's experiments on the Abraxus grossulariata 'Proc.
Entomolog. Soc.' January 6, 1862: these experiments have been confirmed by Mr.
Greening in 'Proc. of the Northern Entomolog. Soc.' July 28, 1862. For the
effects of food on caterpillars see a curious account by M. Michely in 'Bull.
De La Soc. Imp. d'Acclimat.' tome 8 page 563. For analogous facts from Dahlbom
on Hymenoptera see Westwood 'Modern Class. of Insects' volume 2 page 98. See
also Dr. L. Moller 'Die Abhangigkeit der Insecten' 1867 s. 70.)

It would be travelling beyond my proper limits here to discuss how far organic
beings in a state of nature are definitely modified by changed conditions. In
my 'Origin of Species' I have given a brief abstract of the facts bearing on
this point, and have shown the influence of light on the colours of birds, and
of residence near the sea on the lurid tints of insects, and on the succulency
of plants. Mr. Herbert Spencer (23/45. 'The Principles of Biology' volume 2
1866. The present chapters were written before I had read Mr. Herbert
Spencer's work, so that I have not been able to make so much use of it as I
should otherwise probably have done.) has recently discussed with much ability
this whole subject on general grounds. He argues, for instance, that with all
animals the external and internal tissues are differently acted on by the
surrounding conditions, and they invariably differ in intimate structure. So
again the upper and lower surfaces of true leaves, as well as of stems and
petioles, when these assume the function and occupy the position of leaves,
are differently circumstanced with respect to light, etc., and apparently in
consequence differ in structure. But, as Mr. Herbert Spencer admits, it is
most difficult in all such cases to distinguish between the effects of the
definite action of physical conditions and the accumulation through natural
selection of inherited variations which are serviceable to the organism, and
which have arisen independently of the definite action of these conditions.]

Although we are not here concerned with the definite action of the conditions
of life on organisms in a state of nature, I may state that much evidence has
been gained during the last few years on this subject. In the United States,

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