CETACEA. 483 



animals whicli inhabit the globe. Whatever 

 may Iiave been the magnitude of those huge 

 monsters which once moved in the bosom of the 

 primeval ocean, or stalked with gigantic strides 

 across antediluvian plains, and whose scattered 

 remains bear fearful testimony of the convulsions 

 of a former world, certain it is that, at the pre- 

 sent day, the whales of the northern seas are the 

 most colossal of the living animal structures 

 existing on the surface of this planet. 



A cursory survey of the organization of the 

 tribes belonging to this semi-amphibious family, 

 will impress us with the resemblance they bear 

 to fishes ; for they present the same oval outline 

 of the body, the same compact form of the trunk, 

 which is united with the head without an inter- 

 vening neck; the same fin-like shape of the ex- 

 ternal instruments of motion, and the same enor- 

 mous expansion and prolongation of the tail, 

 which is here also, as in fishes, the chief agent in 

 progression. With all this agreement in exter- 

 nal characters, their internal economy is con*- 

 ducted upon a totally different plan ; for although 

 constantly inhabiting the ocean, their vital or- 

 gans are so constructed as to admit of their 

 breathing only the air of the atmosphere, and 

 the consequences which flow from this difference 

 are of great importance. The necessity of aerial 

 respiration compels them to rise, at short inter- 

 vals, to the surface of the water ; and this air, 

 with which they fill their lungs in respiration, 



