INTRODUCTION. 49 



are, with propriety, arranged under the general 

 name of Cetaceous Animals'"'. 



It is not without some violence to our ordinary 

 associations that we can divest the mind of the 

 idea, that the huge Leviathan, and numerous other 

 animals which take their pastime in the deep, are 

 really fishes, as we have been accustomed to regard 

 them; but the circumstance of their being sur- 

 rounded by the waters, is no better calculated to 

 identify them wdth fishes, properly so called, than 

 the similar analogy of birds and quadrupeds, being 

 both smTOunded by the air, is calculated to identify 

 them with each other. Nor can it be urged, as 

 establishing a difference in the latter case which is 

 wanting in the former, that birds are capable of 

 rising in the air, while quadnipeds rest upon the 

 earth ; since a similar difference may be remarked 

 between fishes, properly so called, and the ceta- 

 ceous tribes, that while the former have their abode 

 indiscriminately in any part of the water, the latter 

 are compelled — for respiration — to remain, except 

 for very limited periods, near the top, and even 

 wdth a part of their bodies above the surface. 



By the term Fish, then, is to be understood a 

 vertebrated animal inhabiting the water, with a 

 naked body, or one covered with plates or scales ; 

 moving commonly by means of fins, breathing, if 

 we may use the term, by gills, possessed of a single 



* See a former volume of the Naturalist's Library, devoted 

 to the history of wlialcs, &c. 



D 



