46 Darwin> and after Darwin. 



contrary, it is a general rule that " the less any part of 

 the organization is concerned with special habits, the 

 more important it becomes for classification." Now, 

 from the point of view of special creation it is unin- 

 telligible why unity of ideal should be most manifested 

 by least important structures, whereas from the point of 

 view of evolution it is to be expected that these life- 

 serving structures should have been most liable to diver- 

 gent modification in divergent lines of descent, or in 

 adaptation to different conditions of life, while the trivial 

 or less important characters should have been allowed 

 to remain unmodified. Thus we can now understand 

 why all primitive classifications were wrong in princi- 

 ple when they went upon the assumption that divine 

 ideals were best exhibited by resemblances between 

 life-serving (and therefore adaptive) structures, with 

 the result that whales were classed with fishes, birds 

 with bats, and so on. Nevertheless, these primitive 

 naturalists were quite logical ; for, from the premises 

 furnished by the theory of special creation, it is much 

 more reasonable to expect that unity of ideal should 

 be shown in plainly adaptive characters than in trivial 

 and more or less hidden anatomical characters. More- 

 over, long after biological science had ceased con- 

 sciously to follow any theological theory, the apparent 

 axiom continued to be entertained, that structures of 

 most importance to organisms must also be structures 

 of most importance to systematists. And when at 

 last, in the present century, this was found not to be 

 the case, no reason could be suggested why it was not 

 the case. But now we are able fully to explain this 

 apparent anomaly. 

 Once more, we have seen that aggregates of 



