198 Darwin, and after Darwin. 



In conclusion, it is worth while to remark, with 

 regard to Mr. Wallace's argument from constancy, 

 that, as a matter of fact, utility does not seem to 

 present any greater power in securing " stability of 

 characters " than any other cause of like constancy. 

 Thus, for instance, whatever the causes may have 

 been which have produced and perpetuated the niata 

 breed of cattle, they have certainly produced a won- 

 derful " stability " of a great modification in a wonder- 

 fully short time. And the same has to be said of the 

 ducks in St. James' Park, as well as sundry other cases. 

 On the other hand, when, as in the case of numberless 

 natural species, modification has been undoubtedly 

 produced by natural selection, although the modifica- 

 tion must have had a very much longer time in which 

 to have been fixed by heredity, it is often far from 

 being stable — notwithstanding that Mr. Wallace 

 regards stability as a criterion of specific characters. 

 Indeed — and this is more suggestive still — there even 

 seems to be a kind of inverse proportion between the 

 utility and the stability of a specific character. The ex- 

 planation appears to be [Origin of Species, pp. 130-2), 

 that the more a specific character has been forced on 

 by natural selection on account of its utility, the less 

 time will it have had to become well fixed by heredity 

 before attaining a full development. Moreover, as 

 Darwin adds, in cases where the modification has 

 not only been thus " comparatively recent, " but also 

 " extraordinarily great," the probability is that the 

 parts so modified must have been very variable in the 

 first instance, and so are all the more difficult to 

 render constant by heredity. Thus we see that utility 

 is no better — even if it be so good — a cause of 



