160 CLUES AND SUGGESTIONS CHAP. 



facts to which these belong are guide- 

 posts in the science of Biology. They 

 must have an historical origin, and a 

 meaning, which is not yet thoroughly 

 understood. Let us look at some con- 

 siderations which seem to throw an 

 important light upon them. 



In the first place, it is evident that 

 organic structures, or bits of organic 

 structure, which have no apparent use 

 at all to some individual creatures pos- 

 sessing them, are closely connected with 

 that other case which is much more 

 common the case, namely, of the same 

 organic structures existing in different 

 animals, but which are in them put to 

 entirely different uses. Owen says that 

 even the cetacean pelvis is used, in the 

 meantime, for the attachment of some 

 muscles connected with the generative 

 organs. The five digits of a man's 

 hand, again, are identical in number and 



