Chapter I

Variation under Domestication

Causes of Variability -- Effects of Habit -- Correlation of Growth --

Inheritance -- Character of Domestic Varieties -- Difficulty of

distinguishing between Varieties and Species -- Origin of Domestic

Varieties from one or more Species -- Domestic Pigeons, their Differences

and Origin -- Principle of Selection anciently followed, its Effects --

Methodical and Unconscious Selection -- Unknown Origin of our Domestic

Productions -- Circumstances favourable to Man's power of Selection.

When we look to the individuals of the same variety or sub-variety of our

older cultivated plants and animals, one of the first points which strikes

us, is, that they generally differ much more from each other, than do the

individuals of any one species or variety in a state of nature. When we

reflect on the vast diversity of the plants and animals which have been

cultivated, and which have varied during all ages under the most different

climates and treatment, I think we are driven to conclude that this greater

variability is simply due to our domestic productions having been raised

under conditions of life not so uniform as, and somewhat different from,

those to which the parent-species have been exposed under nature. There

is, also, I think, some probability in the view propounded by Andrew

Knight, that this variability may be partly connected with excess of food.

It seems pretty clear that organic beings must be exposed during several

generations to the new conditions of life to cause any appreciable amount

of variation; and that when the organisation has once begun to vary, it

generally continues to vary for many generations. No case is on record of

a variable being ceasing to be variable under cultivation. Our oldest

cultivated plants, such as wheat, still often yield new varieties: our

oldest domesticated animals are still capable of rapid improvement or

modification.

It has been disputed at what period of life the causes of variability,

whatever they may be, generally act; whether during the early or late

period of development of the embryo, or at the instant of conception.

Geoffroy St. Hilaire's experiments show that unnatural treatment of the

embryo causes monstrosities; and monstrosities cannot be separated by any

clear line of distinction from mere variations. But I am strongly inclined

to suspect that the most frequent cause of variability may be attributed to

the male and female reproductive elements having been affected prior to the

act of conception. Several reasons make me believe in this; but the chief

one is the remarkable effect which confinement or cultivation has on the

functions of the reproductive system; this system appearing to be far more

susceptible than any other part of the organisation, to the action of any

change in the conditions of life. Nothing is more easy than to tame an

animal, and few things more difficult than to get it to breed freely under

confinement, even in the many cases when the male and female unite. How

many animals there are which will not breed, though living long under not

very close confinement in their native country! This is generally

attributed to vitiated instincts; but how many cultivated plants display

the utmost vigour, and yet rarely or never seed! In some few such cases it

has been found out that very trifling changes, such as a little more or

less water at some particular period of growth, will determine whether or

not the plant sets a seed. I cannot here enter on the copious details

which I have collected on this curious subject; but to show how singular

the laws are which determine the reproduction of animals under confinement,

I may just mention that carnivorous animals, even from the tropics, breed

in this country pretty freely under confinement, with the exception of the

plantigrades or bear family; whereas, carnivorous birds, with the rarest

exceptions, hardly ever lay fertile eggs. Many exotic plants have pollen

utterly worthless, in the same exact condition as in the most sterile

hybrids. When, on the one hand, we see domesticated animals and plants,

though often weak and sickly, yet breeding quite freely under confinement;

and when, on the other hand, we see individuals, though taken young from a

state of nature, perfectly tamed, long-lived, and healthy (of which I could

give numerous instances), yet having their reproductive system so seriously

affected by unperceived causes as to fail in acting, we need not be

surprised at this system, when it does act under confinement, acting not

quite regularly, and producing offspring not perfectly like their parents

or variable.

Sterility has been said to be the bane of horticulture; but on this view we

owe variability to the same cause which produces sterility; and variability

is the source of all the choicest productions of the garden. I may add,

that as some organisms will breed most freely under the most unnatural

conditions (for instance, the rabbit and ferret kept in hutches), showing

that their reproductive system has not been thus affected; so will some

animals and plants withstand domestication or cultivation, and vary very

slightly--perhaps hardly more than in a state of nature.

A long list could easily be given of 'sporting plants;' by this term

gardeners mean a single bud or offset, which suddenly assumes a new and

sometimes very different character from that of the rest of the plant.

Such buds can be propagated by grafting, &c., and sometimes by seed. These

'sports' are extremely rare under nature, but far from rare under

cultivation; and in this case we see that the treatment of the parent has

affected a bud or offset, and not the ovules or pollen. But it is the

opinion of most physiologists that there is no essential difference between

a bud and an ovule in their earliest stages of formation; so that, in fact,

'sports' support my view, that variability may be largely attributed to the

ovules or pollen, or to both, having been affected by the treatment of the

parent prior to the act of conception. These cases anyhow show that

variation is not necessarily connected, as some authors have supposed, with

the act of generation.

Seedlings from the same fruit, and the young of the same litter, sometimes

differ considerably from each other, though both the young and the parents,

as Muller has remarked, have apparently been exposed to exactly the same

conditions of life; and this shows how unimportant the direct effects of

the conditions of life are in comparison with the laws of reproduction, and

of growth, and of inheritance; for had the action of the conditions been

direct, if any of the young had varied, all would probably have varied in

the same manner. To judge how much, in the case of any variation, we

should attribute to the direct action of heat, moisture, light, food, &c.,

is most difficult: my impression is, that with animals such agencies have

produced very little direct effect, though apparently more in the case of

plants. Under this point of view, Mr. Buckman's recent experiments on

plants seem extremely valuable. When all or nearly all the individuals

exposed to certain conditions are affected in the same way, the change at

first appears to be directly due to such conditions; but in some cases it

can be shown that quite opposite conditions produce similar changes of

structure. Nevertheless some slight amount of change may, I think, be

attributed to the direct action of the conditions of life--as, in some

cases, increased size from amount of food, colour from particular kinds of

food and from light, and perhaps the thickness of fur from climate.

Habit also has a deciding influence, as in the period of flowering with

plants when transported from one climate to another. In animals it has a

more marked effect; for instance, I find in the domestic duck that the

bones of the wing weigh less and the bones of the leg more, in proportion

to the whole skeleton, than do the same bones in the wild-duck; and I

presume that this change may be safely attributed to the domestic duck

flying much less, and walking more, than its wild parent. The great and

inherited development of the udders in cows and goats in countries where

they are habitually milked, in comparison with the state of these organs in

other countries, is another instance of the effect of use. Not a single

domestic animal can be named which has not in some country drooping ears;

and the view suggested by some authors, that the drooping is due to the

disuse of the muscles of the ear, from the animals not being much alarmed

by danger, seems probable.

There are many laws regulating variation, some few of which can be dimly

seen, and will be hereafter briefly mentioned. I will here only allude to

what may be called correlation of growth. Any change in the embryo or

larva will almost certainly entail changes in the mature animal. In

monstrosities, the correlations between quite distinct parts are very

curious; and many instances are given in Isidore Geoffroy St. Hilaire's

great work on this subject. Breeders believe that long limbs are almost

always accompanied by an elongated head. Some instances of correlation are

quite whimsical; thus cats with blue eyes are invariably deaf; colour and

constitutional peculiarities go together, of which many remarkable cases

could be given amongst animals and plants. From the facts collected by

Heusinger, it appears that white sheep and pigs are differently affected

from coloured individuals by certain vegetable poisons. Hairless dogs have

imperfect teeth; long-haired and coarse-haired animals are apt to have, as

is asserted, long or many horns; pigeons with feathered feet have skin

between their outer toes; pigeons with short beaks have small feet, and

those with long beaks large feet. Hence, if man goes on selecting, and

thus augmenting, any peculiarity, he will almost certainly unconsciously

modify other parts of the structure, owing to the mysterious laws of the

correlation of growth.

The result of the various, quite unknown, or dimly seen laws of variation

is infinitely complex and diversified. It is well worth while carefully to

study the several treatises published on some of our old cultivated plants,

as on the hyacinth, potato, even the dahlia, &c.; and it is really

surprising to note the endless points in structure and constitution in

which the varieties and sub-varieties differ slightly from each other. The

whole organisation seems to have become plastic, and tends to depart in

some small degree from that of the parental type.

Any variation which is not inherited is unimportant for us. But the number

and diversity of inheritable deviations of structure, both those of slight

and those of considerable physiological importance, is endless. Dr.

Prosper Lucas's treatise, in two large volumes, is the fullest and the best

on this subject. No breeder doubts how strong is the tendency to

inheritance: like produces like is his fundamental belief: doubts have

been thrown on this principle by theoretical writers alone. When a

deviation appears not unfrequently, and we see it in the father and child,

we cannot tell whether it may not be due to the same original cause acting

on both; but when amongst individuals, apparently exposed to the same

conditions, any very rare deviation, due to some extraordinary combination

of circumstances, appears in the parent--say, once amongst several million

individuals--and it reappears in the child, the mere doctrine of chances

almost compels us to attribute its reappearance to inheritance. Every one

must have heard of cases of albinism, prickly skin, hairy bodies, &c.,

appearing in several members of the same family. If strange and rare

deviations of structure are truly inherited, less strange and commoner

deviations may be freely admitted to be inheritable. Perhaps the correct

way of viewing the whole subject, would be, to look at the inheritance of

every character whatever as the rule, and non-inheritance as the anomaly.

The laws governing inheritance are quite unknown; no one can say why the

same peculiarity in different individuals of the same species, and in

individuals of different species, is sometimes inherited and sometimes not

so; why the child often reverts in certain characters to its grandfather or

grandmother or other much more remote ancestor; why a peculiarity is often

transmitted from one sex to both sexes or to one sex alone, more commonly

but not exclusively to the like sex. It is a fact of some little

importance to us, that peculiarities appearing in the males of our domestic

breeds are often transmitted either exclusively, or in a much greater

degree, to males alone. A much more important rule, which I think may be

trusted, is that, at whatever period of life a peculiarity first appears,

it tends to appear in the offspring at a corresponding age, though

sometimes earlier. In many cases this could not be otherwise: thus the

inherited peculiarities in the horns of cattle could appear only in the

offspring when nearly mature; peculiarities in the silkworm are known to

appear at the corresponding caterpillar or cocoon stage. But hereditary

diseases and some other facts make me believe that the rule has a wider

extension, and that when there is no apparent reason why a peculiarity

should appear at any particular age, yet that it does tend to appear in the

offspring at the same period at which it first appeared in the parent. I

believe this rule to be of the highest importance in explaining the laws of

embryology. These remarks are of course confined to the first appearance

of the peculiarity, and not to its primary cause, which may have acted on

the ovules or male element; in nearly the same manner as in the crossed

offspring from a short-horned cow by a long-horned bull, the greater length

of horn, though appearing late in life, is clearly due to the male element.

Having alluded to the subject of reversion, I may here refer to a statement

often made by naturalists--namely, that our domestic varieties, when run

wild, gradually but certainly revert in character to their aboriginal

stocks. Hence it has been argued that no deductions can be drawn from

domestic races to species in a state of nature. I have in vain endeavoured

to discover on what decisive facts the above statement has so often and so

boldly been made. There would be great difficulty in proving its truth:

we may safely conclude that very many of the most strongly-marked domestic

varieties could not possibly live in a wild state. In many cases we do not

know what the aboriginal stock was, and so could not tell whether or not

nearly perfect reversion had ensued. It would be quite necessary, in order

to prevent the effects of intercrossing, that only a single variety should

be turned loose in its new home. Nevertheless, as our varieties certainly

do occasionally revert in some of their characters to ancestral forms, it

seems to me not improbable, that if we could succeed in naturalising, or

were to cultivate, during many generations, the several races, for

instance, of the cabbage, in very poor soil (in which case, however, some

effect would have to be attributed to the direct action of the poor soil),

that they would to a large extent, or even wholly, revert to the wild

aboriginal stock. Whether or not the experiment would succeed, is not of

great importance for our line of argument; for by the experiment itself the

conditions of life are changed. If it could be shown that our domestic

varieties manifested a strong tendency to reversion,--that is, to lose

their acquired characters, whilst kept under unchanged conditions, and

whilst kept in a considerable body, so that free intercrossing might check,

by blending together, any slight deviations of structure, in such case, I

grant that we could deduce nothing from domestic varieties in regard to

species. But there is not a shadow of evidence in favour of this view: to

assert that we could not breed our cart and race-horses, long and

short-horned cattle, and poultry of various breeds, and esculent

vegetables, for an almost infinite number of generations, would be opposed

to all experience. I may add, that when under nature the conditions of

life do change, variations and reversions of character probably do occur;

but natural selection, as will hereafter be explained, will determine how

far the new characters thus arising shall be preserved.

When we look to the hereditary varieties or races of our domestic animals

and plants, and compare them with species closely allied together, we

generally perceive in each domestic race, as already remarked, less

uniformity of character than in true species. Domestic races of the same

species, also, often have a somewhat monstrous character; by which I mean,

that, although differing from each other, and from the other species of the

same genus, in several trifling respects, they often differ in an extreme

degree in some one part, both when compared one with another, and more

especially when compared with all the species in nature to which they are

nearest allied. With these exceptions (and with that of the perfect

fertility of varieties when crossed,--a subject hereafter to be discussed),

domestic races of the same species differ from each other in the same

manner as, only in most cases in a lesser degree than, do closely-allied

species of the same genus in a state of nature. I think this must be

admitted, when we find that there are hardly any domestic races, either

amongst animals or plants, which have not been ranked by some competent

judges as mere varieties, and by other competent judges as the descendants

of aboriginally distinct species. If any marked distinction existed

between domestic races and species, this source of doubt could not so

perpetually recur. It has often been stated that domestic races do not

differ from each other in characters of generic value. I think it could be

shown that this statement is hardly correct; but naturalists differ most

widely in determining what characters are of generic value; all such

valuations being at present empirical. Moreover, on the view of the origin

of genera which I shall presently give, we have no right to expect often to

meet with generic differences in our domesticated productions.

When we attempt to estimate the amount of structural difference between the

domestic races of the same species, we are soon involved in doubt, from not

knowing whether they have descended from one or several parent-species.

This point, if it could be cleared up, would be interesting; if, for

instance, it could be shown that the greyhound, bloodhound, terrier,

spaniel, and bull-dog, which we all know propagate their kind so truly,

were the offspring of any single species, then such facts would have great

weight in making us doubt about the immutability of the many very closely

allied and natural species--for instance, of the many foxes--inhabiting

different quarters of the world. I do not believe, as we shall presently

see, that all our dogs have descended from any one wild species; but, in

the case of some other domestic races, there is presumptive, or even

strong, evidence in favour of this view.

It has often been assumed that man has chosen for domestication animals and

plants having an extraordinary inherent tendency to vary, and likewise to

withstand diverse climates. I do not dispute that these capacities have

added largely to the value of most of our domesticated productions; but how

could a savage possibly know, when he first tamed an animal, whether it

would vary in succeeding generations, and whether it would endure other

climates? Has the little variability of the ass or guinea-fowl, or the

small power of endurance of warmth by the rein-deer, or of cold by the

common camel, prevented their domestication? I cannot doubt that if other

animals and plants, equal in number to our domesticated productions, and

belonging to equally diverse classes and countries, were taken from a state

of nature, and could be made to breed for an equal number of generations

under domestication, they would vary on an average as largely as the parent

species of our existing domesticated productions have varied.

In the case of most of our anciently domesticated animals and plants, I do

not think it is possible to come to any definite conclusion, whether they

have descended from one or several species. The argument mainly relied on

by those who believe in the multiple origin of our domestic animals is,

that we find in the most ancient records, more especially on the monuments

of Egypt, much diversity in the breeds; and that some of the breeds closely

resemble, perhaps are identical with, those still existing. Even if this

latter fact were found more strictly and generally true than seems to me to

be the case, what does it show, but that some of our breeds originated

there, four or five thousand years ago? But Mr. Horner's researches have

rendered it in some degree probable that man sufficiently civilized to have

manufactured pottery existed in the valley of the Nile thirteen or fourteen

thousand years ago; and who will pretend to say how long before these

ancient periods, savages, like those of Tierra del Fuego or Australia, who

possess a semi-domestic dog, may not have existed in Egypt?

The whole subject must, I think, remain vague; nevertheless, I may, without

here entering on any details, state that, from geographical and other

considerations, I think it highly probable that our domestic dogs have

descended from several wild species. In regard to sheep and goats I can

form no opinion. I should think, from facts communicated to me by Mr.

Blyth, on the habits, voice, and constitution, &c., of the humped Indian

cattle, that these had descended from a different aboriginal stock from our

European cattle; and several competent judges believe that these latter

have had more than one wild parent. With respect to horses, from reasons

which I cannot give here, I am doubtfully inclined to believe, in

opposition to several authors, that all the races have descended from one

wild stock. Mr. Blyth, whose opinion, from his large and varied stores of

knowledge, I should value more than that of almost any one, thinks that all

the breeds of poultry have proceeded from the common wild Indian fowl

(Gallus bankiva). In regard to ducks and rabbits, the breeds of which

differ considerably from each other in structure, I do not doubt that they

all have descended from the common wild duck and rabbit.

The doctrine of the origin of our several domestic races from several

aboriginal stocks, has been carried to an absurd extreme by some authors.

They believe that every race which breeds true, let the distinctive

characters be ever so slight, has had its wild prototype. At this rate

there must have existed at least a score of species of wild cattle, as many

sheep, and several goats in Europe alone, and several even within Great

Britain. One author believes that there formerly existed in Great Britain

eleven wild species of sheep peculiar to it! When we bear in mind that

Britain has now hardly one peculiar mammal, and France but few distinct

from those of Germany and conversely, and so with Hungary, Spain, &c., but

that each of these kingdoms possesses several peculiar breeds of cattle,

sheep, &c., we must admit that many domestic breeds have originated in

Europe; for whence could they have been derived, as these several countries

do not possess a number of peculiar species as distinct parent-stocks? So

it is in India. Even in the case of the domestic dogs of the whole world,

which I fully admit have probably descended from several wild species, I

cannot doubt that there has been an immense amount of inherited variation.

Who can believe that animals closely resembling the Italian greyhound, the

bloodhound, the bull-dog, or Blenheim spaniel, &c.--so unlike all wild

Canidae--ever existed freely in a state of nature? It has often been

loosely said that all our races of dogs have been produced by the crossing

of a few aboriginal species; but by crossing we can get only forms in some

degree intermediate between their parents; and if we account for our

several domestic races by this process, we must admit the former existence

of the most extreme forms, as the Italian greyhound, bloodhound, bull-dog,

&c., in the wild state. Moreover, the possibility of making distinct races

by crossing has been greatly exaggerated. There can be no doubt that a

race may be modified by occasional crosses, if aided by the careful

selection of those individual mongrels, which present any desired

character; but that a race could be obtained nearly intermediate between

two extremely different races or species, I can hardly believe. Sir J.

Sebright expressly experimentised for this object, and failed. The

offspring from the first cross between two pure breeds is tolerably and

sometimes (as I have found with pigeons) extremely uniform, and everything

seems simple enough; but when these mongrels are crossed one with another

for several generations, hardly two of them will be alike, and then the

extreme difficulty, or rather utter hopelessness, of the task becomes

apparent. Certainly, a breed intermediate between two very distinct breeds

could not be got without extreme care and long-continued selection; nor can

I find a single case on record of a permanent race having been thus formed.

On the Breeds of the Domestic Pigeon. -- Believing that it is always best

to study some special group, I have, after deliberation, taken up domestic

pigeons. I have kept every breed which I could purchase or obtain, and

have been most kindly favoured with skins from several quarters of the

world, more especially by the Hon. W. Elliot from India, and by the Hon. C.

Murray from Persia. Many treatises in different languages have been

published on pigeons, and some of them are very important, as being of

considerably antiquity. I have associated with several eminent fanciers,

and have been permitted to join two of the London Pigeon Clubs. The

diversity of the breeds is something astonishing. Compare the English

carrier and the short-faced tumbler, and see the wonderful difference in

their beaks, entailing corresponding differences in their skulls. The

carrier, more especially the male bird, is also remarkable from the

wonderful development of the carunculated skin about the head, and this is

accompanied by greatly elongated eyelids, very large external orifices to

the nostrils, and a wide gape of mouth. The short-faced tumbler has a beak

in outline almost like that of a finch; and the common tumbler has the

singular and strictly inherited habit of flying at a great height in a

compact flock, and tumbling in the air head over heels. The runt is a bird

of great size, with long, massive beak and large feet; some of the

sub-breeds of runts have very long necks, others very long wings and tails,

others singularly short tails. The barb is allied to the carrier, but,

instead of a very long beak, has a very short and very broad one. The

pouter has a much elongated body, wings, and legs; and its enormously

developed crop, which it glories in inflating, may well excite astonishment

and even laughter. The turbit has a very short and conical beak, with a

line of reversed feathers down the breast; and it has the habit of

continually expanding slightly the upper part of the oesophagus. The

Jacobin has the feathers so much reversed along the back of the neck that

they form a hood, and it has, proportionally to its size, much elongated

wing and tail feathers. The trumpeter and laugher, as their names express,

utter a very different coo from the other breeds. The fantail has thirty

or even forty tail-feathers, instead of twelve or fourteen, the normal

number in all members of the great pigeon family; and these feathers are

kept expanded, and are carried so erect that in good birds the head and

tail touch; the oil-gland is quite aborted. Several other less distinct

breeds might have been specified.

In the skeletons of the several breeds, the development of the bones of the

face in length and breadth and curvature differs enormously. The shape, as

well as the breadth and length of the ramus of the lower jaw, varies in a

highly remarkable manner. The number of the caudal and sacral vertebrae

vary; as does the number of the ribs, together with their relative breadth

and the presence of processes. The size and shape of the apertures in the

sternum are highly variable; so is the degree of divergence and relative

size of the two arms of the furcula. The proportional width of the gape of

mouth, the proportional length of the eyelids, of the orifice of the

nostrils, of the tongue (not always in strict correlation with the length

of beak), the size of the crop and of the upper part of the oesophagus; the

development and abortion of the oil-gland; the number of the primary wing

and caudal feathers; the relative length of wing and tail to each other and

to the body; the relative length of leg and of the feet; the number of

scutellae on the toes, the development of skin between the toes, are all

points of structure which are variable. The period at which the perfect

plumage is acquired varies, as does the state of the down with which the

nestling birds are clothed when hatched. The shape and size of the eggs

vary. The manner of flight differs remarkably; as does in some breeds the

voice and disposition. Lastly, in certain breeds, the males and females

have come to differ to a slight degree from each other.

Altogether at least a score of pigeons might be chosen, which if shown to

an ornithologist, and he were told that they were wild birds, would

certainly, I think, be ranked by him as well-defined species. Moreover, I

do not believe that any ornithologist would place the English carrier, the

short-faced tumbler, the runt, the barb, pouter, and fantail in the same

genus; more especially as in each of these breeds several truly-inherited

sub-breeds, or species as he might have called them, could be shown him.

Great as the differences are between the breeds of pigeons, I am fully

convinced that the common opinion of naturalists is correct, namely, that

all have descended from the rock-pigeon (Columba livia), including under

this term several geographical races or sub-species, which differ from each

other in the most trifling respects. As several of the reasons which have

led me to this belief are in some degree applicable in other cases, I will

here briefly give them. If the several breeds are not varieties, and have

not proceeded from the rock-pigeon, they must have descended from at least

seven or eight aboriginal stocks; for it is impossible to make the present

domestic breeds by the crossing of any lesser number: how, for instance,

could a pouter be produced by crossing two breeds unless one of the

parent-stocks possessed the characteristic enormous crop? The supposed

aboriginal stocks must all have been rock-pigeons, that is, not breeding or

willingly perching on trees. But besides C. livia, with its geographical

sub-species, only two or three other species of rock-pigeons are known; and

these have not any of the characters of the domestic breeds. Hence the

supposed aboriginal stocks must either still exist in the countries where

they were originally domesticated, and yet be unknown to ornithologists;

and this, considering their size, habits, and remarkable characters, seems

very improbable; or they must have become extinct in the wild state. But

birds breeding on precipices, and good fliers, are unlikely to be

exterminated; and the common rock-pigeon, which has the same habits with

the domestic breeds, has not been exterminated even on several of the

smaller British islets, or on the shores of the Mediterranean. Hence the

supposed extermination of so many species having similar habits with the

rock-pigeon seems to me a very rash assumption. Moreover, the several

above-named domesticated breeds have been transported to all parts of the

world, and, therefore, some of them must have been carried back again into

their native country; but not one has ever become wild or feral, though the

dovecot-pigeon, which is the rock-pigeon in a very slightly altered state,

has become feral in several places. Again, all recent experience shows

that it is most difficult to get any wild animal to breed freely under

domestication; yet on the hypothesis of the multiple origin of our pigeons,

it must be assumed that at least seven or eight species were so thoroughly

domesticated in ancient times by half-civilized man, as to be quite

prolific under confinement.

An argument, as it seems to me, of great weight, and applicable in several

other cases, is, that the above-specified breeds, though agreeing generally

in constitution, habits, voice, colouring, and in most parts of their

structure, with the wild rock-pigeon, yet are certainly highly abnormal in

other parts of their structure: we may look in vain throughout the whole

great family of Columbidae for a beak like that of the English carrier, or

that of the short-faced tumbler, or barb; for reversed feathers like those

of the jacobin; for a crop like that of the pouter; for tail-feathers like

those of the fantail. Hence it must be assumed not only that

half-civilized man succeeded in thoroughly domesticating several species,

but that he intentionally or by chance picked out extraordinarily abnormal

species; and further, that these very species have since all become extinct

or unknown. So many strange contingencies seem to me improbable in the

highest degree.

Some facts in regard to the colouring of pigeons well deserve

consideration. The rock-pigeon is of a slaty-blue, and has a white rump

(the Indian sub-species, C. intermedia of Strickland, having it bluish);

the tail has a terminal dark bar, with the bases of the outer feathers

externally edged with white; the wings have two black bars; some

semi-domestic breeds and some apparently truly wild breeds have, besides

the two black bars, the wings chequered with black. These several marks do

not occur together in any other species of the whole family. Now, in every

one of the domestic breeds, taking thoroughly well-bred birds, all the

above marks, even to the white edging of the outer tail-feathers, sometimes

concur perfectly developed. Moreover, when two birds belonging to two

distinct breeds are crossed, neither of which is blue or has any of the

above-specified marks, the mongrel offspring are very apt suddenly to

acquire these characters; for instance, I crossed some uniformly white

fantails with some uniformly black barbs, and they produced mottled brown

and black birds; these I again crossed together, and one grandchild of the

pure white fantail and pure black barb was of as beautiful a blue colour,

with the white rump, double black wing-bar, and barred and white-edged

tail-feathers, as any wild rock-pigeon! We can understand these facts, on

the well-known principle of reversion to ancestral characters, if all the

domestic breeds have descended from the rock-pigeon. But if we deny this,

we must make one of the two following highly improbable suppositions.

Either, firstly, that all the several imagined aboriginal stocks were

coloured and marked like the rock-pigeon, although no other existing

species is thus coloured and marked, so that in each separate breed there

might be a tendency to revert to the very same colours and markings. Or,

secondly, that each breed, even the purest, has within a dozen or, at most,

within a score of generations, been crossed by the rock-pigeon: I say

within a dozen or twenty generations, for we know of no fact countenancing

the belief that the child ever reverts to some one ancestor, removed by a

greater number of generations. In a breed which has been crossed only once

with some distinct breed, the tendency to reversion to any character

derived from such cross will naturally become less and less, as in each

succeeding generation there will be less of the foreign blood; but when

there has been no cross with a distinct breed, and there is a tendency in

both parents to revert to a character, which has been lost during some

former generation, this tendency, for all that we can see to the contrary,

may be transmitted undiminished for an indefinite number of generations.

These two distinct cases are often confounded in treatises on inheritance.

Lastly, the hybrids or mongrels from between all the domestic breeds of

pigeons are perfectly fertile. I can state this from my own observations,

purposely made on the most distinct breeds. Now, it is difficult, perhaps

impossible, to bring forward one case of the hybrid offspring of two

animals clearly distinct being themselves perfectly fertile. Some authors

believe that long-continued domestication eliminates this strong tendency

to sterility: from the history of the dog I think there is some

probability in this hypothesis, if applied to species closely related

together, though it is unsupported by a single experiment. But to extend

the hypothesis so far as to suppose that species, aboriginally as distinct

as carriers, tumblers, pouters, and fantails now are, should yield

offspring perfectly fertile, inter se, seems to me rash in the extreme.

From these several reasons, namely, the improbability of man having

formerly got seven or eight supposed species of pigeons to breed freely

under domestication; these supposed species being quite unknown in a wild

state, and their becoming nowhere feral; these species having very abnormal

characters in certain respects, as compared with all other Columbidae,

though so like in most other respects to the rock-pigeon; the blue colour

and various marks occasionally appearing in all the breeds, both when kept

pure and when crossed; the mongrel offspring being perfectly fertile;--from

these several reasons, taken together, I can feel no doubt that all our

domestic breeds have descended from the Columba livia with its geographical

sub-species.

In favour of this view, I may add, firstly, that C. livia, or the

rock-pigeon, has been found capable of domestication in Europe and in

India; and that it agrees in habits and in a great number of points of

structure with all the domestic breeds. Secondly, although an English

carrier or short-faced tumbler differs immensely in certain characters from

the rock-pigeon, yet by comparing the several sub-breeds of these breeds,

more especially those brought from distant countries, we can make an almost

perfect series between the extremes of structure. Thirdly, those

characters which are mainly distinctive of each breed, for instance the

wattle and length of beak of the carrier, the shortness of that of the

tumbler, and the number of tail-feathers in the fantail, are in each breed

eminently variable; and the explanation of this fact will be obvious when

we come to treat of selection. Fourthly, pigeons have been watched, and

tended with the utmost care, and loved by many people. They have been

domesticated for thousands of years in several quarters of the world; the

earliest known record of pigeons is in the fifth Aegyptian dynasty, about

3000 B.C., as was pointed out to me by Professor Lepsius; but Mr. Birch

informs me that pigeons are given in a bill of fare in the previous

dynasty. In the time of the Romans, as we hear from Pliny, immense prices

were given for pigeons; 'nay, they are come to this pass, that they can

reckon up their pedigree and race.' Pigeons were much valued by Akber Khan

in India, about the year 1600; never less than 20,000 pigeons were taken

with the court. 'The monarchs of Iran and Turan sent him some very rare

birds;' and, continues the courtly historian, 'His Majesty by crossing the

breeds, which method was never practised before, has improved them

astonishingly.' About this same period the Dutch were as eager about

pigeons as were the old Romans. The paramount importance of these

considerations in explaining the immense amount of variation which pigeons

have undergone, will be obvious when we treat of Selection. We shall then,

also, see how it is that the breeds so often have a somewhat monstrous

character. It is also a most favourable circumstance for the production of

distinct breeds, that male and female pigeons can be easily mated for life;

and thus different breeds can be kept together in the same aviary.

I have discussed the probable origin of domestic pigeons at some, yet quite

insufficient, length; because when I first kept pigeons and watched the

several kinds, knowing well how true they bred, I felt fully as much

difficulty in believing that they could ever have descended from a common

parent, as any naturalist could in coming to a similar conclusion in regard

to the many species of finches, or other large groups of birds, in nature.

One circumstance has struck me much; namely, that all the breeders of the

various domestic animals and the cultivators of plants, with whom I have

ever conversed, or whose treatises I have read, are firmly convinced that

the several breeds to which each has attended, are descended from so many

aboriginally distinct species. Ask, as I have asked, a celebrated raiser

of Hereford cattle, whether his cattle might not have descended from long

horns, and he will laugh you to scorn. I have never met a pigeon, or

poultry, or duck, or rabbit fancier, who was not fully convinced that each

main breed was descended from a distinct species. Van Mons, in his

treatise on pears and apples, shows how utterly he disbelieves that the

several sorts, for instance a Ribston-pippin or Codlin-apple, could ever

have proceeded from the seeds of the same tree. Innumerable other examples

could be given. The explanation, I think, is simple: from long-continued

study they are strongly impressed with the differences between the several

races; and though they well know that each race varies slightly, for they

win their prizes by selecting such slight differences, yet they ignore all

general arguments, and refuse to sum up in their minds slight differences

accumulated during many successive generations. May not those naturalists

who, knowing far less of the laws of inheritance than does the breeder, and

knowing no more than he does of the intermediate links in the long lines of

descent, yet admit that many of our domestic races have descended from the

same parents--may they not learn a lesson of caution, when they deride the

idea of species in a state of nature being lineal descendants of other

species?

Selection. -- Let us now briefly consider the steps by which domestic races

have been produced, either from one or from several allied species. Some

little effect may, perhaps, be attributed to the direct action of the

external conditions of life, and some little to habit; but he would be a

bold man who would account by such agencies for the differences of a dray

and race horse, a greyhound and bloodhound, a carrier and tumbler pigeon.

One of the most remarkable features in our domesticated races is that we

see in them adaptation, not indeed to the animal's or plant's own good, but

to man's use or fancy. Some variations useful to him have probably arisen

suddenly, or by one step; many botanists, for instance, believe that the

fuller's teazle, with its hooks, which cannot be rivalled by any mechanical

contrivance, is only a variety of the wild Dipsacus; and this amount of

change may have suddenly arisen in a seedling. So it has probably been

with the turnspit dog; and this is known to have been the case with the

ancon sheep. But when we compare the dray-horse and race-horse, the

dromedary and camel, the various breeds of sheep fitted either for

cultivated land or mountain pasture, with the wool of one breed good for

one purpose, and that of another breed for another purpose; when we compare

the many breeds of dogs, each good for man in very different ways; when we

compare the game-cock, so pertinacious in battle, with other breeds so

little quarrelsome, with 'everlasting layers' which never desire to sit,

and with the bantam so small and elegant; when we compare the host of

agricultural, culinary, orchard, and flower-garden races of plants, most

useful to man at different seasons and for different purposes, or so

beautiful in his eyes, we must, I think, look further than to mere

variability. We cannot suppose that all the breeds were suddenly produced

as perfect and as useful as we now see them; indeed, in several cases, we

know that this has not been their history. The key is man's power of

accumulative selection: nature gives successive variations; man adds them

up in certain directions useful to him. In this sense he may be said to

make for himself useful breeds.

The great power of this principle of selection is not hypothetical. It is

certain that several of our eminent breeders have, even within a single

lifetime, modified to a large extent some breeds of cattle and sheep. In

order fully to realise what they have done, it is almost necessary to read

several of the many treatises devoted to this subject, and to inspect the

animals. Breeders habitually speak of an animal's organisation as

something quite plastic, which they can model almost as they please. If I

had space I could quote numerous passages to this effect from highly

competent authorities. Youatt, who was probably better acquainted with the

works of agriculturalists than almost any other individual, and who was

himself a very good judge of an animal, speaks of the principle of

selection as 'that which enables the agriculturist, not only to modify the

character of his flock, but to change it altogether. It is the magician's

wand, by means of which he may summon into life whatever form and mould he

pleases.' Lord Somerville, speaking of what breeders have done for sheep,

says:- 'It would seem as if they had chalked out upon a wall a form perfect

in itself, and then had given it existence.' That most skilful breeder,

Sir John Sebright, used to say, with respect to pigeons, that 'he would

produce any given feather in three years, but it would take him six years

to obtain head and beak.' In Saxony the importance of the principle of

selection in regard to merino sheep is so fully recognised, that men follow

it as a trade: the sheep are placed on a table and are studied, like a

picture by a connoisseur; this is done three times at intervals of months,

and the sheep are each time marked and classed, so that the very best may

ultimately be selected for breeding.

What English breeders have actually effected is proved by the enormous

prices given for animals with a good pedigree; and these have now been

exported to almost every quarter of the world. The improvement is by no

means generally due to crossing different breeds; all the best breeders are

strongly opposed to this practice, except sometimes amongst closely allied

sub-breeds. And when a cross has been made, the closest selection is far

more indispensable even than in ordinary cases. If selection consisted

merely in separating some very distinct variety, and breeding from it, the

principle would be so obvious as hardly to be worth notice; but its

importance consists in the great effect produced by the accumulation in one

direction, during successive generations, of differences absolutely

inappreciable by an uneducated eye--differences which I for one have vainly

attempted to appreciate. Not one man in a thousand has accuracy of eye and

judgment sufficient to become an eminent breeder. If gifted with these

qualities, and he studies his subject for years, and devotes his lifetime

to it with indomitable perseverance, he will succeed, and may make great

improvements; if he wants any of these qualities, he will assuredly fail.

Few would readily believe in the natural capacity and years of practice

requisite to become even a skilful pigeon-fancier.

The same principles are followed by horticulturists; but the variations are

here often more abrupt. No one supposes that our choicest productions have

been produced by a single variation from the aboriginal stock. We have

proofs that this is not so in some cases, in which exact records have been

kept; thus, to give a very trifling instance, the steadily-increasing size

of the common gooseberry may be quoted. We see an astonishing improvement

in many florists' flowers, when the flowers of the present day are compared

with drawings made only twenty or thirty years ago. When a race of plants

is once pretty well established, the seed-raisers do not pick out the best

plants, but merely go over their seed-beds, and pull up the 'rogues,' as

they call the plants that deviate from the proper standard. With animals

this kind of selection is, in fact, also followed; for hardly any one is so

careless as to allow his worst animals to breed.

In regard to plants, there is another means of observing the accumulated

effects of selection--namely, by comparing the diversity of flowers in the

different varieties of the same species in the flower-garden; the diversity

of leaves, pods, or tubers, or whatever part is valued, in the

kitchen-garden, in comparison with the flowers of the same varieties; and

the diversity of fruit of the same species in the orchard, in comparison

with the leaves and flowers of the same set of varieties. See how

different the leaves of the cabbage are, and how extremely alike the

flowers; how unlike the flowers of the heartsease are, and how alike the

leaves; how much the fruit of the different kinds of gooseberries differ in

size, colour, shape, and hairiness, and yet the flowers present very slight

differences. It is not that the varieties which differ largely in some one

point do not differ at all in other points; this is hardly ever, perhaps

never, the case. The laws of correlation of growth, the importance of

which should never be overlooked, will ensure some differences; but, as a

general rule, I cannot doubt that the continued selection of slight

variations, either in the leaves, the flowers, or the fruit, will produce

races differing from each other chiefly in these characters.

It may be objected that the principle of selection has been reduced to

methodical practice for scarcely more than three-quarters of a century; it

has certainly been more attended to of late years, and many treatises have

been published on the subject; and the result, I may add, has been, in a

corresponding degree, rapid and important. But it is very far from true

that the principle is a modern discovery. I could give several references

to the full acknowledgment of the importance of the principle in works of

high antiquity. In rude and barbarous periods of English history choice

animals were often imported, and laws were passed to prevent their

exportation: the destruction of horses under a certain size was ordered,

and this may be compared to the 'roguing' of plants by nurserymen. The

principle of selection I find distinctly given in an ancient Chinese

encyclopaedia. Explicit rules are laid down by some of the Roman classical

writers. From passages in Genesis, it is clear that the colour of domestic

animals was at that early period attended to. Savages now sometimes cross

their dogs with wild canine animals, to improve the breed, and they

formerly did so, as is attested by passages in Pliny. The savages in South

Africa match their draught cattle by colour, as do some of the Esquimaux

their teams of dogs. Livingstone shows how much good domestic breeds are

valued by the negroes of the interior of Africa who have not associated

with Europeans. Some of these facts do not show actual selection, but they

show that the breeding of domestic animals was carefully attended to in

ancient times, and is now attended to by the lowest savages. It would,

indeed, have been a strange fact, had attention not been paid to breeding,

for the inheritance of good and bad qualities is so obvious.

At the present time, eminent breeders try by methodical selection, with a

distinct object in view, to make a new strain or sub-breed, superior to

anything existing in the country. But, for our purpose, a kind of

Selection, which may be called Unconscious, and which results from every

one trying to possess and breed from the best individual animals, is more

important. Thus, a man who intends keeping pointers naturally tries to get

as good dogs as he can, and afterwards breeds from his own best dogs, but

he has no wish or expectation of permanently altering the breed.

Nevertheless I cannot doubt that this process, continued during centuries,

would improve and modify any breed, in the same way as Bakewell, Collins,

&c., by this very same process, only carried on more methodically, did

greatly modify, even during their own lifetimes, the forms and qualities of

their cattle. Slow and insensible changes of this kind could never be

recognised unless actual measurements or careful drawings of the breeds in

question had been made long ago, which might serve for comparison. In some

cases, however, unchanged or but little changed individuals of the same

breed may be found in less civilised districts, where the breed has been

less improved. There is reason to believe that King Charles's spaniel has

been unconsciously modified to a large extent since the time of that

monarch. Some highly competent authorities are convinced that the setter

is directly derived from the spaniel, and has probably been slowly altered

from it. It is known that the English pointer has been greatly changed

within the last century, and in this case the change has, it is believed,

been chiefly effected by crosses with the fox-hound; but what concerns us

is, that the change has been effected unconsciously and gradually, and yet

so effectually, that, though the old Spanish pointer certainly came from

Spain, Mr. Borrow has not seen, as I am informed by him, any native dog in

Spain like our pointer.

By a similar process of selection, and by careful training, the whole body

of English racehorses have come to surpass in fleetness and size the parent

Arab stock, so that the latter, by the regulations for the Goodwood Races,

are favoured in the weights they carry. Lord Spencer and others have shown

how the cattle of England have increased in weight and in early maturity,

compared with the stock formerly kept in this country. By comparing the

accounts given in old pigeon treatises of carriers and tumblers with these

breeds as now existing in Britain, India, and Persia, we can, I think,

clearly trace the stages through which they have insensibly passed, and

come to differ so greatly from the rock-pigeon.

Youatt gives an excellent illustration of the effects of a course of

selection, which may be considered as unconsciously followed, in so far

that the breeders could never have expected or even have wished to have

produced the result which ensued--namely, the production of two distinct

strains. The two flocks of Leicester sheep kept by Mr. Buckley and Mr.

Burgess, as Mr. Youatt remarks, 'have been purely bred from the original

stock of Mr. Bakewell for upwards of fifty years. There is not a suspicion

existing in the mind of any one at all acquainted with the subject that the

owner of either of them has deviated in any one instance from the pure

blood of Mr. Bakewell's flock, and yet the difference between the sheep

possessed by these two gentlemen is so great that they have the appearance

of being quite different varieties.'

If there exist savages so barbarous as never to think of the inherited

character of the offspring of their domestic animals, yet any one animal

particularly useful to them, for any special purpose, would be carefully

preserved during famines and other accidents, to which savages are so

liable, and such choice animals would thus generally leave more offspring

than the inferior ones; so that in this case there would be a kind of

unconscious selection going on. We see the value set on animals even by

the barbarians of Tierra del Fuego, by their killing and devouring their

old women, in times of dearth, as of less value than their dogs.

In plants the same gradual process of improvement, through the occasional

preservation of the best individuals, whether or not sufficiently distinct

to be ranked at their first appearance as distinct varieties, and whether

or not two or more species or races have become blended together by

crossing, may plainly be recognised in the increased size and beauty which

we now see in the varieties of the heartsease, rose, pelargonium, dahlia,

and other plants, when compared with the older varieties or with their

parent-stocks. No one would ever expect to get a first-rate heartsease or

dahlia from the seed of a wild plant. No one would expect to raise a

first-rate melting pear from the seed of a wild pear, though he might

succeed from a poor seedling growing wild, if it had come from a

garden-stock. The pear, though cultivated in classical times, appears,

from Pliny's description, to have been a fruit of very inferior quality. I

have seen great surprise expressed in horticultural works at the wonderful

skill of gardeners, in having produced such splendid results from such poor

materials; but the art, I cannot doubt, has been simple, and, as far as the

final result is concerned, has been followed almost unconsciously. It has

consisted in always cultivating the best known variety, sowing its seeds,

and, when a slightly better variety has chanced to appear, selecting it,

and so onwards. But the gardeners of the classical period, who cultivated

the best pear they could procure, never thought what splendid fruit we

should eat; though we owe our excellent fruit, in some small degree, to

their having naturally chosen and preserved the best varieties they could

anywhere find.

A large amount of change in our cultivated plants, thus slowly and

unconsciously accumulated, explains, as I believe, the well-known fact,

that in a vast number of cases we cannot recognise, and therefore do not

know, the wild parent-stocks of the plants which have been longest

cultivated in our flower and kitchen gardens. If it has taken centuries or

thousands of years to improve or modify most of our plants up to their

present standard of usefulness to man, we can understand how it is that

neither Australia, the Cape of Good Hope, nor any other region inhabited by

quite uncivilised man, has afforded us a single plant worth culture. It is

not that these countries, so rich in species, do not by a strange chance

possess the aboriginal stocks of any useful plants, but that the native

plants have not been improved by continued selection up to a standard of

perfection comparable with that given to the plants in countries anciently

civilised.

In regard to the domestic animals kept by uncivilised man, it should not be

overlooked that they almost always have to struggle for their own food, at

least during certain seasons. And in two countries very differently

circumstanced, individuals of the same species, having slightly different

constitutions or structure, would often succeed better in the one country

than in the other, and thus by a process of 'natural selection,' as will

hereafter be more fully explained, two sub-breeds might be formed. This,

perhaps, partly explains what has been remarked by some authors, namely,

that the varieties kept by savages have more of the character of species

than the varieties kept in civilised countries.

On the view here given of the all-important part which selection by man has

played, it becomes at once obvious, how it is that our domestic races show

adaptation in their structure or in their habits to man's wants or fancies.

We can, I think, further understand the frequently abnormal character of

our domestic races, and likewise their differences being so great in

external characters and relatively so slight in internal parts or organs.

Man can hardly select, or only with much difficulty, any deviation of

structure excepting such as is externally visible; and indeed he rarely

cares for what is internal. He can never act by selection, excepting on

variations which are first given to him in some slight degree by nature.

No man would ever try to make a fantail, till he saw a pigeon with a tail

developed in some slight degree in an unusual manner, or a pouter till he

saw a pigeon with a crop of somewhat unusual size; and the more abnormal or

unusual any character was when it first appeared, the more likely it would

be to catch his attention. But to use such an expression as trying to make

a fantail, is, I have no doubt, in most cases, utterly incorrect. The man

who first selected a pigeon with a slightly larger tail, never dreamed what

the descendants of that pigeon would become through long-continued, partly

unconscious and partly methodical selection. Perhaps the parent bird of

all fantails had only fourteen tail-feathers somewhat expanded, like the

present Java fantail, or like individuals of other and distinct breeds, in

which as many as seventeen tail-feathers have been counted. Perhaps the

first pouter-pigeon did not inflate its crop much more than the turbit now

does the upper part of its oesophagus,--a habit which is disregarded by all

fanciers, as it is not one of the points of the breed.

Nor let it be thought that some great deviation of structure would be

necessary to catch the fancier's eye: he perceives extremely small

differences, and it is in human nature to value any novelty, however

slight, in one's own possession. Nor must the value which would formerly

be set on any slight differences in the individuals of the same species, be

judged of by the value which would now be set on them, after several breeds

have once fairly been established. Many slight differences might, and

indeed do now, arise amongst pigeons, which are rejected as faults or

deviations from the standard of perfection of each breed. The common goose

has not given rise to any marked varieties; hence the Thoulouse and the

common breed, which differ only in colour, that most fleeting of

characters, have lately been exhibited as distinct at our poultry-shows.

I think these views further explain what has sometimes been noticed--namely

that we know nothing about the origin or history of any of our domestic

breeds. But, in fact, a breed, like a dialect of a language, can hardly be

said to have had a definite origin. A man preserves and breeds from an

individual with some slight deviation of structure, or takes more care than

usual in matching his best animals and thus improves them, and the improved

individuals slowly spread in the immediate neighbourhood. But as yet they

will hardly have a distinct name, and from being only slightly valued,

their history will be disregarded. When further improved by the same slow

and gradual process, they will spread more widely, and will get recognised

as something distinct and valuable, and will then probably first receive a

provincial name. In semi-civilised countries, with little free

communication, the spreading and knowledge of any new sub-breed will be a

slow process. As soon as the points of value of the new sub-breed are once

fully acknowledged, the principle, as I have called it, of unconscious

selection will always tend,--perhaps more at one period than at another, as

the breed rises or falls in fashion,--perhaps more in one district than in

another, according to the state of civilisation of the inhabitants--slowly

to add to the characteristic features of the breed, whatever they may be.

But the chance will be infinitely small of any record having been preserved

of such slow, varying, and insensible changes.

I must now say a few words on the circumstances, favourable, or the

reverse, to man's power of selection. A high degree of variability is

obviously favourable, as freely giving the materials for selection to work

on; not that mere individual differences are not amply sufficient, with

extreme care, to allow of the accumulation of a large amount of

modification in almost any desired direction. But as variations manifestly

useful or pleasing to man appear only occasionally, the chance of their

appearance will be much increased by a large number of individuals being

kept; and hence this comes to be of the highest importance to success. On

this principle Marshall has remarked, with respect to the sheep of parts of

Yorkshire, that 'as they generally belong to poor people, and are mostly in

small lots, they never can be improved.' On the other hand, nurserymen,

from raising large stocks of the same plants, are generally far more

successful than amateurs in getting new and valuable varieties. The

keeping of a large number of individuals of a species in any country

requires that the species should be placed under favourable conditions of

life, so as to breed freely in that country. When the individuals of any

species are scanty, all the individuals, whatever their quality may be,

will generally be allowed to breed, and this will effectually prevent

selection. But probably the most important point of all, is, that the

animal or plant should be so highly useful to man, or so much valued by

him, that the closest attention should be paid to even the slightest

deviation in the qualities or structure of each individual. Unless such

attention be paid nothing can be effected. I have seen it gravely

remarked, that it was most fortunate that the strawberry began to vary just

when gardeners began to attend closely to this plant. No doubt the

strawberry had always varied since it was cultivated, but the slight

varieties had been neglected. As soon, however, as gardeners picked out

individual plants with slightly larger, earlier, or better fruit, and

raised seedlings from them, and again picked out the best seedlings and

bred from them, then, there appeared (aided by some crossing with distinct

species) those many admirable varieties of the strawberry which have been

raised during the last thirty or forty years.

In the case of animals with separate sexes, facility in preventing crosses

is an important element of success in the formation of new races,--at

least, in a country which is already stocked with other races. In this

respect enclosure of the land plays a part. Wandering savages or the

inhabitants of open plains rarely possess more than one breed of the same

species. Pigeons can be mated for life, and this is a great convenience to

the fancier, for thus many races may be kept true, though mingled in the

same aviary; and this circumstance must have largely favoured the

improvement and formation of new breeds. Pigeons, I may add, can be

propagated in great numbers and at a very quick rate, and inferior birds

may be freely rejected, as when killed they serve for food. On the other

hand, cats, from their nocturnal rambling habits, cannot be matched, and,

although so much valued by women and children, we hardly ever see a

distinct breed kept up; such breeds as we do sometimes see are almost

always imported from some other country, often from islands. Although I do

not doubt that some domestic animals vary less than others, yet the rarity

or absence of distinct breeds of the cat, the donkey, peacock, goose, &c.,

may be attributed in main part to selection not having been brought into

play: in cats, from the difficulty in pairing them; in donkeys, from only

a few being kept by poor people, and little attention paid to their

breeding; in peacocks, from not being very easily reared and a large stock

not kept; in geese, from being valuable only for two purposes, food and

feathers, and more especially from no pleasure having been felt in the

display of distinct breeds.

To sum up on the origin of our Domestic Races of animals and plants. I

believe that the conditions of life, from their action on the reproductive

system, are so far of the highest importance as causing variability. I do

not believe that variability is an inherent and necessary contingency,

under all circumstances, with all organic beings, as some authors have

thought. The effects of variability are modified by various degrees of

inheritance and of reversion. Variability is governed by many unknown

laws, more especially by that of correlation of growth. Something may be

attributed to the direct action of the conditions of life. Something must

be attributed to use and disuse. The final result is thus rendered

infinitely complex. In some cases, I do not doubt that the intercrossing

of species, aboriginally distinct, has played an important part in the

origin of our domestic productions. When in any country several domestic

breeds have once been established, their occasional intercrossing, with the

aid of selection, has, no doubt, largely aided in the formation of new

sub-breeds; but the importance of the crossing of varieties has, I believe,

been greatly exaggerated, both in regard to animals and to those plants

which are propagated by seed. In plants which are temporarily propagated

by cuttings, buds, &c., the importance of the crossing both of distinct

species and of varieties is immense; for the cultivator here quite

disregards the extreme variability both of hybrids and mongrels, and the

frequent sterility of hybrids; but the cases of plants not propagated by

seed are of little importance to us, for their endurance is only temporary.

Over all these causes of Change I am convinced that the accumulative action

of Selection, whether applied methodically and more quickly, or

unconsciously and more slowly, but more efficiently, is by far the

predominant Power.