In lieu of an abstract, here is a brief excerpt of the content:

1 2 CHAPTER II. VARIATION UNDER NATURE. 3 Variability-Individual differences-Doubtful species-Wide ranging , much diffused, and common species vary most-Species of the larger genera in any country vary more than the species of the smaller genera-Many of the species of the larger genera resemble varieties in being very closely, but unequally, related to each other, and in having restricted ranges. 3:d in each country vary more frequently than 3:f species, vary most-Species of the larger genera in each 4 BEFOREapplying the principles arrived at in the last chapter to organic beings in a state of nature, we must briefly discuss whether these latter are subject to any variation. 5 To treat this subject at all properly, a long catalogue of dry facts should be given; but these I shall reserve for my future work. 5:d facts ought to be 5:f subject properly Ifor a future 6 Nor shall I here discuss the various definitions which have been given of the term species. 7 No one definition has as yet satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of a species. 7:f has satisfied 8 Generally the term includes the unknown element of a distinct act of creation. 9 The term "variety" is almost equally difficult to define; but here community of descent is almost universally implied, though it can rarely be proved. 10 We have also what are called monstrosities; but they graduate into varieties. 11 By a monstrosity I presume is meant some considerable deviation of structure in one part, either injurious to or not useful to the species, and not generally propagated. I I:C part, generally injurious to or not useful to the species. I rid structure, generally II:f injurious, or not 12 Some authors use the term "variation" in a technical sense, as implying a modification directly due to the physical conditions of life; and "variations" in this sense are supposed not to be 120 inherited: but who can say that the dwarfed condition of shells in the brackish waters of the Baltic, or dwarfed plants on Alpine summits, or the thicker fur of an animal from far northwards , would not in some cases be inherited for at least some few generations? and in this case I presume that the form would be called a variety. I2:1 inherited; but/least a few I2.I :c[~] It may perhaps be doubted whether monstrosities, or such sudden and great deviations of structure as we occasionally see in our domestic productions, more especially with plants, are ever permanently propagated in a state of nature. I2.I:d may be doubted whether sudden and great deviations of structure such as I2.I:/ sudden and considerable deviations I2.2:C Monsters are very apt to be sterile; and almost every part of every organic being, at least with animals, is so beautifully related to its complex conditions of life that it seems as improbable that any part should have been suddenly produced perfect, as that a complex machine should have been invented by man in a perfect state. I2.2:d Almost/being is I2.3-6:c I have not, at least, been able to find good cases of species in a state of nature presenting modifications of structure resembling monstrosities observed in allied forms. 4 If such have occurred, their perpetuation will have been due to their beneficial nature, so that natural selection will have come into play. 5 Many cases are known of plants which regularly produce on different branches, or on the circumference and in the centre of umbels, &c., flowers of a widely different structure; and if the plant ceased to produce flowers of the one kind, a great change might perhaps suddenly be effected in the specific character; but then we do not at present know by what steps, or for what good, a plant produces two kinds of flowers. 6 With cultivated plants, in the few cases known of a variety habitually bearing flowers or fruit slightly different from each other, the production of the variety has been sudden. I 2.3-6:[d] I2.6.I:d Under domestication monstrosities often occur which are comparable with normal structures. I2.6.I:e which resemble normal structures in widely different animals . I2.6.I:1 monstrosities sometimes occur I2.6.2-3:d Thus pigs have often been born with a sort of proboscis like that of...

Share