nerves, muscles, arteries, are developed in proportion to the change of external form.

Besides selection by death, in bisexual animals (illegible)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 charms1. 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, (whose) instincts (are) best developed, will rear more young, probably possessing her good qualities, and a greater number will thus (be) 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] sexual characters. Introduce here contrast with Lamarck,-absurdity of habit, or chance?? or external conditions, making a woodpecker adapted to tree2.

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

1 Here we have the two types of sexual selection discussed in the Origin, Ed. i. pp. 88 et seq., vi. pp. 108 et seq.

It is not obvious why the author objects to "chance" or "external conditions making a woodpecker." 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 passage the two ? refer.

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 all1. Gladiolus, Crinum, Calceolaria2 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 very general. Some nearest species will not cross (crocus, some heath (?)), some genera cross readily (fowls and grouse, peacock &c.). Hybrids no ways monstrous quite perfect except secretions5 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]. Will analogy throw any light

The meaning is "That sterility is not universal is admitted by all." 2 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.

3 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 peacock. 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.

Ackermann (Ber. d. Vereins f. Naturkunde zu Kassel, 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.

No doubt the sexual cells are meant. I do not know on what evidence it is stated that the mule has bred.

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

on the fact of the supposed races of nature being sterile, though none of the domestic ones are? Mr Herbert (and) Koelreuter have shown external differences will not guide one in knowing whether hybrids will be fertile or not, but the chief circumstance is constitutional differences1, such as being adapted to different climate or soil, differences which [must] probably affect the whole body of the organism and not any one part. Now wild animals, taken out of their natural conditions, seldom breed. I do not refer to shows or to Zoological Societies where many animals unite, but (do not?) 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,-ferrets2. 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 (it) 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 (an) effect on their mind and a special case.

But turning to plants we find same class of facts. I do not refer to seeds not ripening, perhaps the com

found that they were sterile together. See the case of the red and blue Anagallis given from Gärtner in the Origin, Ed. i. p. 247, vi. p. 368.

In the Origin, Ed. i. p. 258, where the author speaks of constitutional differences in this connexion, he specifies that they are confined to the reproductive system.

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.

1

monest 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,-Linnæus about alpine plants. American bog plants,-pollen in exactly same state as in hybrids,―same in geraniums. Persian and Chinese1 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. There is here gradation (in) sterility and then parts, like diseases, are transmitted hereditarily. We cannot assign any cause why the Pontic Azalea produces plenty of pollen and not American3, why common lilac seeds and not Persian, we see no difference in healthiness. We know not on what circumstances these facts depend, why ferret breeds, and cheetah, elephant and pig in India will not.

Now in crossing it is certain every peculiarity in form and constitution is transmitted: an alpine plant transmits its alpine tendency to its offspring, an an American plant its American-bog constitution, and (with) animals, those peculiarities, on which5 when placed out of their natural conditions they are incapable of breeding; and moreover they transmit every part of their constitution, their

1 Lindley's remark is quoted in the Origin, Ed. i. p. 9. Linnæus' 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.

2

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.

3 I have not come across this case in the author's works.

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.

5 This sentence should run 66 on which depends their incapacity to breed in unnatural conditions."

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 bred1. Variation depends on change of condition and selection2, as far as man's systematic or unsystematic selection (has) gone; he takes external form, has little power from ignorance over internal invisible constitutional differences. Races which have long been domesticated, and have much varied, are precisely those which were capable of bearing great changes, whose constitutions 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 (illegible) has been (illegible) 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 tried3. 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 head1.

1 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.

2 The author doubtless refers to the change produced by the summation of variation by means of selection.

The meaning of this sentence is made clear by a passage in the мs. 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.

♦ This passage is to some extent a repetition of a previous one and may