Characters as Adaptive and Specific. 225 



and if it be not counteracted by reversion, then 

 the proportion of the new variety to the original 

 form will increase till it approaches indefinitely 

 near to equality V Now even Mr. Wallace himself 

 allows that this must be the case ; and thinks that in 

 these considerations we may find, an explanation of 

 the existence of certain definite varieties, such as 

 the melanic form of the jaguar, the brindled or ring- 

 eyed guillemot, &c. But, on the other hand, he 

 thinks that such varieties must always be unstable, 

 and continually produced in varying proportions 

 from the parent forms. We need not, however, 

 wait to dispute this arbitrary assumption, because 

 we can see that it fails, even as an assumption, in 

 all cases where the superadded influence of isolation 

 is concerned. Here there is nothing to intercept 

 the original tendency to divergent evolution, which 

 arises directly out of the initially different average 

 of qualities presented by the isolated section of the 

 species, as compared with the rest of that species ^. 



' Habit and Intelligence, p. 241. 



^ Allusion may here again be made to the case of the niata cattle. 

 For here is a case where a very extreme variety is certainly not unstable, 

 nor produced in varying proportions from the parent form. Moreover, 

 as we have seen in the preceding chapter, this almost monstrous 

 variety most probably originated as an individual sport— being after- 

 wards maintained and multiplied for a time by artificial selection. Now, 

 whether or not this was the case, we can very well see that it may have 

 been. Hence it will serve to illustrate another possibility touching the 

 origin and maintenance of useless specific characters. For what is 

 to prevent an individual congenital variation of any kind (provided it 

 be not harmful) from perpetuating itself as a " varietal," and eventually, 

 should offspring become sufficiently numerous, a " specific character " ? 

 There is nothing to prevent this, save panmixia, or the presence of free 

 intercrossing. But, as we shall see in the next division of this treatise, 

 there are in nature many forms of isolation. Hence, as often as a small 

 number of individuals may have experienced isolation in any of its forms, 



11. Q 



