STUDIES IN ANIMAL LIFE. 89 



An unscientific Pliny might group animals accord- 

 ing to their habitat; but when it was known that 

 whales, though living in the water and swimming 

 like fishes, were in reality constructed like air- 

 breathing quadrupeds when it was known that 

 animals differing so widely as bees, birds, bats, and 

 flying squirrels, or as otters, seals, and cuttlefish, 

 lived together in the same element, it became ob- 

 vious that such a principle of arrangement could 

 lead to no practical result. Nor would it suffice to 

 class animals according to their modes of feeding, 

 since in all classes there are samples of each mode. 

 Equally unsatisfactory would be external form 

 the seal and the whale resembling fishes, the worm 

 resembling the eel, and the eel the serpent. 



Two things were necessary : first, that the struc- 

 ture of various animals should be minutely studied 

 and described which is equivalent to reading the 

 books to be classified ; and, secondly, that some ar- 

 tificial method should be devised of so arranging the 

 immense mass of details as to enable them to be re- 

 membered, and also to enable fresh discoveries readi- 

 ly to find a place in the system. We may be per- 

 fectly familiar with the contents of a book, yet 

 wholly at a loss where to place it. If we have to 

 catalogue Hegel's Philosophy of History, for exam- 

 ple, it becomes a difficult question whether to place 

 it under the rubric of philosophy, or under that of 

 history. To decide this point, we must have some 

 system of classification. 



