LAWS OF VARIATION 123 



tain some light. First let me make some preliminary remarks. If, 

 in our domestic animals, any part or the whole animal be neg- 

 lected, and no selection be applied, that part (for instance, the 

 comb in the Dorking fowl) or the whole breed will cease to have 

 a uniform character; and the breed may be said to be degenerat- 

 ing. In rudimentary organs, and in those which have been but 

 little specialized for any particular purpose, and perhaps in poly- 

 morphic groups, we see a nearly parallel case; for in such cases 

 natural selection either has not or cannot have come into full 

 play, and thus the organization is left in a fluctuating condition. 

 But what here more particularly concerns us is, that those points 

 in our domestic animals, which at the present time are under- 

 going rapid change by continued selection, are also eminently 

 liable to variation. Look at the individuals of the same breed of 

 the pigeon, and see what a prodigious amount of difference there 

 is in the beaks of tumblers, in the beaks and wattle of carriers, 

 in the carriage and tail of fantails, etc., these being the points 

 now mainly attended to by English fanciers. Even in the same 

 sub-breed, as in that of the short-faced tumbler, it is notoriously 

 difficult to breed nearly perfect birds, many departing widely from 

 the standard. There may truly be said to be a constant struggle 

 going on between, on the one hand, the tendency to reversion to 

 a less perfect state, as well as an innate tendency to new varia- 

 tions, and, on the other hand, the power of steady selection to 

 keep the breed true. In the long-run selection gains the day, and 

 we do not expect to fail so completely as to breed a bird as 

 coarse as a common tumbler pigeon from a good short-faced 

 strain. But as long as selection is rapidly going on, much vari- 

 ability in the parts undergoing modification may always be ex- 

 pected. 



Now let us turn to nature. When a part has been developed in 

 an extraordinary manner in any one species, compared with the 

 other species of the same genus, we may conclude that this part 

 has undergone an extraordinary amount of modification since the 

 period when the several species branched off from the common 

 progenitor of the genus. This period will seldom be remote in 

 any extreme degree, as^species rarely endure ior more than one 

 geological period. An extraordinary amount of modification im- 

 plies an unusually large and long-continued amount of variability, 

 which has continually been accumulated by natural selection for 

 the benefit of the species. But as the variability of the extraor- 

 dinarily developed part or organ has been so great and long- 

 continued, within a period not excessively remote, we might, as 



