346 Miscellaneous. 



The speaker then analyzed the process of selection by which the 

 domesticated breeds had been produced from the wild Rock Pigeon, 

 and he showed its possibility to depend upon laws which hold good 

 for all species, viz. 1. That every species tends to vary. 2. That 

 variations are capable of hereditary transmission. The second law is 

 well understood ; but the speaker adverted to the miscomprehension 

 which appears to prevail regarding the first, and showed that the 

 variation of a species is by no means an adaptation to conditions in 

 the sense in which that phrase is commonly used. Pigeon fanciers, 

 in fact, subject their pigeons to a complete uniformity of conditions ; 

 but while the similarly used feet, legs, skull, sacral vertebrae, tail- 

 feathers, oil-gland, and crop undergo the most extraordinary modifi- 

 cations, on the other hand, the wings, whose use is hardly ever 

 permitted to the choice breeds, have hitherto shown no sign of 

 diminution. Man has not as yet been able to determine a variation ; 

 he only favours those which arise spontaneously, i.e. are determined 

 by unknown conditions. 



It must be admitted that, by selection, a species may be made to 

 give rise experimentally to excessively different modifications ; and 

 the next question is, do causes adequate to exert selection exist in 

 nature? On this point, the speaker referred his audience to Mr. 

 Darwin's chapter on the struggle for existence, as affording ample 

 satisfactory proof that such adequate natural causes do exist. 



There can be no doubt that just as man cherishes the varieties he 

 wishes to preserve, and destroys those he does not care about, so 

 Nature (even if we consider the physical world as a mere mechanism) 

 must tend to cherish those varieties which are better fitted to work 

 harmoniously with the conditions she offers, and to destroy the rest. 



There seems to be no doubt, then, that modifications equivalent in 

 extent to the four breeds of pigeons might be developed from a 

 species by natural causes ; and therefore, if it can be shown that 

 these breeds have all the characters which are ever found in species, 

 Mr. Darwin's case would be complete. Unfortunately, however, 

 there is as yet no proof that, by selection, modifications having the 

 physiological character of species (i.e. whose offspring are incapable 

 of propagation, inter se) have ever been produced from a common 

 stock. 



No doubt the numerous indirect arguments brought forward by 

 Mr. Darwin to weaken the force of this objection are of great weight ; 

 no doubt it cannot be proved that all species give rise to hybrids 

 infertile inter se ; no doubt (so far as the speaker's private convic- 

 tion went) a well-conducted series of experiments very probably 

 would yield us derivatives from a common stock, whose offspring 

 should be infertile inter se ; but we must deal with facts as they 

 stand, and at present it must be admitted that Mr. Darwin's theory 

 does not account for all the phenomena exhibited by species : and, 

 so far, falls short of being a perfectly satisfactory theory. 



Nevertheless, the speaker expressed his sense of the extremely 

 high value to be attached to Mr. Darwin's hypothesis, and avowed 

 his own conviction that the following it out must ultimately lead us 

 to the detection of the laws which have governed the origin of species. 



