152 LAWS OF VARIATION. Chap. V. 



presumption is that it is of high importance to that 

 species ; nevertheless the part in this case is eminently 

 liable to variation. Why should this be so ? On the 

 view that each species has been independently created, 

 with all its parts as we now see them, I can see no 

 explanation. But on the view that groups of species 

 have descended from other species, and have been mo- 

 dified through natural selection, I think we can obtain 

 some light. In our domestic animals, if any part, or 

 the whole animal, be neglected and no selection be ap- 

 plied, that part (for instance, the comb in the Dorking 

 fowl) or the whole breed will cease to have a nearly 

 uniform character. The breed will then be said to have 

 degenerated. In rudimentary organs, and in those 

 winch have been but little specialised for any particular 

 purpose, and perhaps in polymorphic groups, we see a 

 nearly parallel natural case ; for in such cases natural 

 selection either has not or cannot come into full play, 

 and thus the organisation is left in a fluctuating condi- 

 tion. But what here more especially concerns us is, 

 that in our domestic animals those points, which at the 

 present time are undergoing rapid change by continued 

 selection, are also eminently liable to variation. Look 

 at the breeds of the pigeon ; see what a prodigious 

 amount of difference there is in the beak of the differ- 

 ent tumblers, in the beak and wattle of the different 

 carriers, in the carriage and tail of our fantails, &c, 

 these being the points now mainly attended to by Eng- 

 lish fanciers. Even in the sub-breeds, as in the short- 

 faced tumbler, it is notoriously difficult to breed them 

 nearly to perfection, and frequently individuals are born 

 which depart widely from the standard. There may be 

 truly said to be a constant struggle going on between, 

 on the one hand, the tendency to reversion to a less 

 modified state, as well as an innate tendency to further 



