6 THE MAMMALIA. 



ing of the subject? Can those who know the 

 Mammalia of our day, in all the various phe- 

 nomena of their life and the differences in their 

 structure, be said to be fully enlightened as to the 

 causes and connection of all these facts ? As this 

 has generally been taken for granted, zoology has 

 hitherto been stigmatised by the senseless appella- 

 tion of ' a descriptive science ; ' for, in fact, it was 

 not considered to possess the character of a science 

 that inquires into a causal connection. As if a 

 science could exist without having an observing as 

 well as a descriptive part ! 



The descriptive zoologist need not in any way 

 trouble himself or be astonished at anything. 

 When, however, he has to take into consideration 

 the scientific results of recent times, he will have 

 to pause before a series of specially striking phe- 

 nomena. This will happen, for instance, when he 

 is about to make a preliminary comparison of the 

 Mammalia with the rest of the Vertebrates, for he 

 will want transition forms between the former and 

 the latter. Buffon's opinion, that by carefully 

 observing two organisms, however different, an un- 

 interrupted series of transition forms will always 

 be found, did not long hold good in face of our 

 more strict systematic arrangement. The link 



