4-72 EDWAED 13. POULTON. 



of any stage, but it is of immense value in affording sugges- 

 tions as to what the stage has been. This remarkable animal 

 is doubtless a direct descendant of a type which would give us 

 sure knowledge as to the origin of many peculiarly mammalian 

 features. But individual specialisation has accompanied the 

 long course of descent, so that even in this lowest of living 

 mammals, structures which are characteristic of the class, and 

 of which Me might fairly expect to see the origin, are assumed 

 as it were — used as the raw material for further structural 

 modification. Upon this subject I hope to write on a future 

 occasion and to give details ; I mention it now to show the 

 uncertainty of interpretating the origin of a structure from 

 data of Comparative Anatomy only. And yet such data som.e- 

 times afford valuable suggestions, capable of verification, and 

 often of a kind that could not be given by any other study. 



