18 THE MAMMALIA. 



form, that is, upon the inexplicable sovereignty of 

 the idea of type. Even though parallel groups 

 such as the repetition of different orders of the 

 Mammalia within the group of Marsupials, the 

 repetition of the habitus of the .Rodents in the 

 Insectivora were observed and discussed, still the 

 contented zoologist did no more than enter these 

 observations into his book; and remarks such as 

 those made by Goethe and d' Alton remained with- 

 out result. What position Darwin took as regards 

 the idea of convergence, has already been stated. 

 His school, too, endeavoured at first to account for 

 the homologies exclusively by inheritance, and, on 

 the other hand, regarded the effects of adaptation 

 almost wholly as differentiation. Even that 

 extremely interesting adaptation as a means 

 of defence mimicry and, moreover, the ease 

 where the species in danger finds immunity and 

 protection in feigning a resemblance with the 

 species not endangered, did not lead to any 

 generalisation of the inquiry. Still, some striking 

 phenomena of convergence were observed, and 

 others that had long since been known, but not 

 carefully considered, were inquired into more 

 particularly. Among these is Fritz Miiller's 

 admirable analysis of the arrangements by which 



