The Foundations of the Origin of Species Part 3

{57} _Origin_, Ed. i. p. 74, vi. p. 91. "It has been observed that the trees now growing on ... ancient Indian mounds ... display the same beautiful diversity and proportion of kinds as in the surrounding virgin forests."

{58} The simile of the wedge occurs in the _Origin_, Ed. i. p. 67; it is deleted in Darwin's copy of the first edition: it does not occur in Ed. vi.

The unavoidable effect of this that many of every species are destroyed either in egg or [young or mature (the former state the more common)]. In the course of a thousand generations infinitesimally small differences must inevitably tell{59}; when unusually cold winter, or hot or dry summer comes, then out of the whole body of individuals of any species, if there be the smallest differences in their structure, habits, instincts [senses], health &c, will on an average tell; as conditions change a rather larger proportion will be preserved: so if the chief check to increase falls on seeds or eggs, so will, in the course of 1000 generations or ten thousand, those seeds (like one with down to fly{60}) which fly furthest and get scattered most ultimately rear most plants, and such small differences tend to be hereditary like shades of expression in human countenance. So if one parent fish deposits its egg in infinitesimally different circ.u.mstances, as in rather shallower or deeper water &c., it will then tell.

{59} In a rough summary at the close of the Essay, occur the words:--"Every creature lives by a struggle, smallest grain in balance must tell."

{60} Cf. _Origin_, Ed. i. p. 77, vi. p. 94.

Let hares{61} increase very slowly from change of climate affecting peculiar plants, and some other rabbit decrease in same proportion [let this unsettle organisation of], a canine animal, who formerly derived its chief sustenance by springing on rabbits or running them by scent, must decrease too and might thus readily become exterminated. But if its form varied very slightly, the long legged fleet ones, during a thousand years being selected, and the less fleet rigidly destroyed must, if no law of nature be opposed to it, alter forms.

{61} This is a repet.i.tion of what is given at p. 6.

Remember how soon Bakewell on the same principle altered cattle and Western, sheep,--carefully avoiding a cross (pigeons) with any breed.

We cannot suppose that one plant tends to vary in fruit and another in flower, and another in flower and foliage,--some have been selected for both fruit and flower: that one animal varies in its covering and another not,--another in its milk. Take any organism and ask what is it useful for and on that point it will be found to vary,--cabbages in their leaf,--corn in size : pigeons in peculiarities approaching to monsters. This requires consideration,--should be introduced in first chapter if it holds, I believe it does. It is hypothetical at best{62}.

{62} Compare _Origin_, Ed. i. p. 41, vi. p. 47. "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."

Nature's variation far less, but such selection far more rigid and scrutinising. Man's races not [even so well] only not better adapted to conditions than other races, but often not one race adapted to its conditions, as man keeps and propagates some alpine plants in garden.

Nature lets

Besides selection by death, in bis.e.xual animals the selection in time of fullest vigour, namely struggle of males; even in animals which pair there seems a surplus and a battle, possibly as in man more males produced than females, struggle of war or charms{63}.

Hence that male which at that time is in fullest vigour, or best armed with arms or ornaments of its species, will gain in hundreds of generations some small advantage and transmit such characters to its offspring. So in female rearing its young, the most vigorous and skilful and industrious, instincts prepared for the struggle of nature. Compared to man using a male alone of good breed. This latter section only of limited application, applies to variation of [specific] s.e.xual characters.

Introduce here contrast with Lamarck,--absurdity of habit, or chance??

or external conditions, making a woodp.e.c.k.e.r adapted to tree{64}.

{63} Here we have the two types of s.e.xual selection discussed in the _Origin_, Ed. i. pp. 88 et seq., vi. pp. 108 et seq.

{64} It is not obvious why the author objects to "chance" or "external conditions making a woodp.e.c.k.e.r." He allows that variation is ultimately referable to conditions and that the nature of the connexion is unknown, i.e. that the result is fortuitous. It is not clear in the original to how much of the pa.s.sage the two ? refer.

Before considering difficulties of theory of selection let us consider character of the races produced, as now explained, by nature. Conditions have varied slowly and the organisms best adapted in their whole course of life to the changed conditions have always been selected,--man selects small dog and afterwards gives it profusion of food,--selects a long-backed and short-legged breed and gives it no particular exercise to suit this function &c. &c. In ordinary cases nature has not allowed her race to be contaminated with a cross of another race, and agriculturists know how difficult they find always to prevent this,--effect would be trueness. This character and sterility when crossed, and generally a greater amount of difference, are two main features, which distinguish domestic races from species.

[Sterility not universal admitted by all{65}. _Gladiolus_, _Crinum_, _Calceolaria_{66} must be species if there be such a thing. Races of dogs and oxen: but certainly very general; indeed a gradation of sterility most perfect{67} very general. Some nearest species will not cross (crocus, some heath ), some genera cross readily (fowls{68} and grouse, peac.o.c.k &c.). Hybrids no ways monstrous quite perfect except secretions{69} hence even the mule has bred,--character of sterility, especially a few years ago thought very much more universal than it now is, has been thought the distinguishing character; indeed it is obvious if all forms freely crossed, nature would be a chaos. But the very gradation of the character, even if it always existed in some degree which it does not, renders it impossible as marks those suppose distinct as species{70}]. Will a.n.a.logy throw any light on the fact of the supposed races of nature being sterile, though none of the domestic ones are? Mr Herbert breed, and others will never unite, but to wild animals caught and kept _quite tame_ left loose and well fed about houses and living many years. Hybrids produced almost as readily as pure breds. St Hilaire great distinction of tame and domestic,--elephants,--ferrets{72}.

Reproductive organs not subject to disease in Zoological Garden.

Dissection and microscope show that hybrid is in exactly same condition as another animal in the intervals of breeding season, or those animals which taken wild and _not bred_ in domesticity, remain without breeding their whole lives. It should be observed that so far from domesticity being unfavourable in itself makes more fertile: [when animal is domesticated and breeds, productive power increased from more food and selection of fertile races]. As far as animals go might be thought

{65} The meaning is "That sterility is not universal is admitted by all."

{66} See _Var. under Dom._, Ed. 2, i. p. 388, where the garden forms of _Gladiolus_ and _Calceolaria_ are said to be derived from crosses between distinct species. Herbert's hybrid _Crinums_ are discussed in the _Origin_, Ed. i. p. 250, vi. p. 370. It is well known that the author believed in a multiple origin of domestic dogs.

{67} The argument from gradation in sterility is given in the _Origin_, Ed. i. pp. 248, 255, vi. pp. 368, 375. In the _Origin_, I have not come across the cases mentioned, viz. crocus, heath, or grouse and fowl or peac.o.c.k. For sterility between closely allied species, see _Origin_, Ed. i. p. 257, vi. p. 377. In the present essay the author does not distinguish between fertility between species and the fertility of the hybrid offspring, a point on which he insists in the _Origin_, Ed. i. p. 245, vi. p. 365.

{68} Ackermann (_Ber. d. Vereins f. Naturkunde zu Ka.s.sel_, 1898, p.

23) quotes from Gloger that a cross has been effected between a domestic hen and a _Tetrao tetrix_; the offspring died when three days old.

{69} No doubt the s.e.xual cells are meant. I do not know on what evidence it is stated that the mule has bred.

{70} The sentence is all but illegible. I think that the author refers to forms usually ranked as varieties having been marked as species when it was found that they were sterile together. See the case of the red and blue _Anagallis_ given from Gartner in the _Origin_, Ed. i. p. 247, vi. p. 368.

{71} In the _Origin_, Ed. i. p. 258, where the author speaks of const.i.tutional differences in this connexion, he specifies that they are confined to the reproductive system.

{72} The sensitiveness of the reproductive system to changed conditions is insisted on in the _Origin_, Ed. i. p. 8, vi. p. 10.

The ferret is mentioned, as being prolific in captivity, in _Var.

under Dom._, Ed. 2, ii. p. 90.

But turning to plants we find same cla.s.s of facts. I do not refer to seeds not ripening, perhaps the commonest cause, but to plants not setting, which either is owing to some imperfection of ovule or pollen.

Lindley says sterility is the [curse] bane of all propagators,--Linnaeus about alpine plants. American bog plants,--pollen in exactly same state as in hybrids,--same in geraniums. Persian and Chinese{73} lilac will not seed in Italy and England. Probably double plants and all fruits owe their developed parts primarily to sterility and extra food thus applied{74}. There is here gradation sterility and then parts, like diseases, are transmitted hereditarily. We cannot a.s.sign any cause why the Pontic Azalea produces plenty of pollen and not American{75}, why common lilac seeds and not Persian, we see no difference in healthiness.

We know not on what circ.u.mstances these facts depend, why ferret breeds, and cheetah{76}, elephant and pig in India will not.

{73} Lindley's remark is quoted in the _Origin_, Ed. i. p. 9.

Linnaeus' remark is to the effect that Alpine plants tend to be sterile under cultivation (see _Var. under Dom._, Ed. 2, ii. p.

147). In the same place the author speaks of peat-loving plants being sterile in our gardens,--no doubt the American bog-plants referred to above. On the following page (p. 148) the sterility of the lilac (_Syringa persica_ and _chinensis_) is referred to.

{74} The author probably means that the increase in the petals is due to a greater food supply being available for them owing to sterility. See the discussion in _Var. under Dom._, Ed. 2, ii. p.

151. It must be noted that doubleness of the flower may exist without noticeable sterility.

{75} I have not come across this case in the author's works.

{76} For the somewhat doubtful case of the cheetah (_Felis jubata_) see _Var. under Dom._, Ed. 2, ii. p. 133. I do not know to what fact "pig in India" refers.

Now in crossing it is certain every peculiarity in form and const.i.tution is transmitted: an alpine plant transmits its alpine tendency to its offspring, an American plant its American-bog const.i.tution, and animals, those peculiarities, on which{77} when placed out of their natural conditions they are incapable of breeding; and moreover they transmit every part of their const.i.tution, their respiration, their pulse, their instinct, which are all suddenly modified, can it be wondered at that they are incapable of breeding? I think it may be truly said it would be more wonderful if they did. But it may be asked why have not the recognised varieties, supposed to have been produced through the means of man, [not refused to breed] have all bred{78}.

Variation depends on change of condition and selection{79}, as far as man's systematic or unsystematic selection gone; he takes external form, has little power from ignorance over internal invisible const.i.tutional differences. Races which have long been domesticated, and have much varied, are precisely those which were capable of bearing great changes, whose const.i.tutions were adapted to a diversity of climates. Nature changes slowly and by degrees. According to many authors probably breeds of dogs are another case of modified species freely crossing. There is no variety which has been adapted to peculiar soil or situation for a thousand years and another rigorously adapted to another, till such can be produced, the question is not tried{80}. Man in past ages, could transport into different climates, animals and plants which would freely propagate in such new climates. Nature could effect, with selection, such changes slowly, so that precisely those animals which are adapted to submit to great changes have given rise to diverse races,--and indeed great doubt on this head{81}.

{77} This sentence should run "on which depends their incapacity to breed in unnatural conditions."

{78} This sentence ends in confusion: it should clearly close with the words "refused to breed" in place of the bracket and the present concluding phrase.

{79} The author doubtless refers to the change produced by the _summation_ of variation by means of selection.

{80} The meaning of this sentence is made clear by a pa.s.sage in the MS. of 1844:--"Until man selects two varieties from the same stock, adapted to two climates or to other different external conditions, and confines each rigidly for one or several thousand years to such conditions, always selecting the individuals best adapted to them, he cannot be said to have even commenced the experiment." That is, the attempt to produce mutually sterile domestic breeds.

{81} This pa.s.sage is to some extent a repet.i.tion of a previous one and may have been intended to replace an earlier sentence. I have thought it best to give both. In the _Origin_, Ed. i. p. 141, vi.

p. 176, the author gives his opinion that the power of resisting diverse conditions, seen in man and his domestic animals, is an example "of a very common flexibility of const.i.tution."

Before leaving this subject well to observe that it was shown that a certain amount of variation is consequent on mere act of reproduction, both by buds and s.e.xually,--is vastly increased when parents exposed for some generations to new conditions{82}, and we now find that many animals when exposed for first time to very new conditions, are

{82} In the _Origin_, Ed. i. Chs. I. and V., the author does not admit reproduction, apart from environment, as being a cause of variation. With regard to the c.u.mulative effect of new conditions there are many pa.s.sages in the _Origin_, Ed. i. e.g. pp. 7, 12, vi.

pp. 8, 14.

{83} As already pointed out, this is the important principle investigated in the author's _Cross and Self-Fertilisation_.

Professor Bateson has suggested to me that the experiments should be repeated with gametically pure individuals.

_Difficulties on theory of selection_{84}. It may be objected such perfect organs as eye and ear, could never be formed, in latter less difficulty as gradations more perfect; at first appears monstrous and to end appears difficulty. But think of gradation, even now manifest, (Tibia and Fibula). Everyone will allow if every fossil preserved, gradation infinitely more perfect; for possibility of selection a perfect gradation is required. Different groups of structure, slight gradation in each group,--every a.n.a.logy renders it probable that intermediate forms have existed. Be it remembered what strange metamorphoses; part of eye, not directly connected with vision, might come to be [thus used] gradually worked in for this end,--swimming bladder by gradation of structure is admitted to belong to the ear system,--rattlesnake. [Woodp.e.c.k.e.r best adapted to climb.] In some cases gradation not possible,--as vertebrae,--actually vary in domestic animals,--less difficult if growth followed. Looking to whole animals, a bat formed not for flight{85}. Suppose we had flying fish{86} and not one of our now called flying fish preserved, who would have guessed intermediate habits. Woodp.e.c.k.e.rs and tree-frogs both live in countries where no trees{87}.

{84} In the _Origin_ a chapter is given up to "difficulties on theory": the discussion in the present essay seems slight even when it is remembered how small a s.p.a.ce is here available. For _Tibia_ &c. see p. 48.

{85} This may be interpreted "The general structure of a bat is the same as that of non-flying mammals."