ISOLATION 365 



external factor, and by reason of some inherent peculiarity of 

 erovvth : some variation which, once started on such and such 

 a trend, has gone on developing that peculiarity. And what 

 is true of this particular bone is true also of a hundred skeletal 

 details. The changes in the relative position of the vomer, with 

 regard to the palatines and pterygoids, and its varying stages 

 of degeneration, ending, in many groups, by complete suppres- 

 sion, affords another illustration of what would seem to be a 

 process of development and degradation independent of the 

 action of natural selection. 



