fully convinced of the general occurrence of variation in nature as he afterwards became. The above passage in the text possibly suggests that at this time he laid more stress on sports or mutations than was afterwards the case.
50
The author may possibly have taken the case of the woodpecker from Buffon, Histoire Nat. des Oiseaux, T. vii. p. 3, 1780, where however it is treated from a different point of view. He uses it more than once, see for instance Origin, Ed. i. pp. 3, 60, 184, vi. pp. 3, 76, 220. The passage in the text corresponds with a discussion on the woodpecker and the mistletoe in Origin, Ed. i. p. 3, vi. p. 3.
51
This illustration occurs in the Origin, Ed. i. pp. 90, 91, vi. pp. 110, 111.
52
See Origin, Ed. i. p. 83, vi. p. 102, where the word Creator is replaced by Nature.
53
Note in the original. “Good place to introduce, saying reasons hereafter to be given, how far I extend theory, say to all mammalia – reasons growing weaker and weaker.”
54
See Origin, Ed. i. pp. 62, 63, vi. p. 77, where similar reference is made to De Candolle; for Malthus see Origin, p. 5.
55
This may possibly refer to the amount of destruction going on. See Origin, Ed. i. p. 68, vi. p. 84, where there is an estimate of a later date as to death-rate of birds in winter. “Calculate robins” probably refers to a calculation of the rate of increase of birds under favourable conditions.
56
In the Origin, Ed. i. pp. 64, 65, vi. p. 80, he instances cattle and horses and certain plants in S. America and American species of plants in India, and further on, as unexpected effects of changed conditions, the enclosure of a heath, and the relation between the fertilisation of clover and the presence of cats (Origin, Ed. i. p. 74, vi. p. 91).
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.
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.
61
This is a repetition of what is given at p. 6.
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.”
63
Here we have the two types of sexual 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 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.
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 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.
68
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.
69
No doubt the sexual 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 Gärtner in the Origin, Ed. i. p. 247, vi. p. 368.
71
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.
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.
73
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.
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.
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 passage 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 passage is to some extent a repetition 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,
