2 A HISTORY OF FISHES 



further fostered by the editors of popular works on natural 

 history, who devote three-quarters of the available pages to 

 the mammals and birds, crowding the unfortunate lower 

 animals — every bit as interesting and quite often of extreme 

 beauty — into a few short chapters at the end. 



A fish, therefore, is a vertebrate, and one specially adapted 

 for a purely aquatic life. But this definition is still inadequate, 



Fig. I. CETACEAN AND FISH COMPARED. 



A. Common Dolphin {Delphinus^delphis) ; B.^Mackerel Shark [Isurus oxyrhyn- 

 chus). Both much reduced. 



for all the vertebrates living in the water are not fishes. What 

 of the Whales, Seals, Otters, Newts, and Frogs? In my official 

 capacity I am sometimes asked to settle arguments, occasionally 

 backed by substantial stakes, as to whether or no a Whale is 

 a fish. Here there is the same fish-like body, the fin-like fore 

 limbs or paddles, and often a fin in the middle of the back 

 (Fig. I a). Nevertheless, a Whale is not a fish, but a mammal. 

 A close examination of its skin reveals the presence of a few 

 vestigial hairs in the region of the muzzle, the structure of the 

 paddle is quite unlike that of the fish's fin (Fig. 2), being in all 



