INTRODUCTION. 57 



habits of other animals, and of fishes, the analogies 

 are not less perfect than with respect to their struc- 

 ture. The latter move in their native element as 

 we do in ours : they use, like all other animals, 

 certain means of self-defence and of attack ; they 

 smell, see, hear, and feel ; they furnish numer- 

 ous evidences of instinct, and not a few, perhaps, 

 in its very highest range ; they respire ; they circu- 

 late their fluids; they digest their aliment; they 

 pei'petuate their species : and can a knowledge of 

 the peculiarity of the processes by which they do 

 all this, be supposed to be superfluous to one en- 

 gaged in investigating the corresponding processes 

 in other forms of animated nature ? Certainly not. 

 Let us cease, then, to regard fishes as standing, as 

 it were, alone in the creation, and constituting a 

 tribe of uninteresting beings, the study of the eco- 

 nomy of which is meagre in itself, and has only a 

 very remote and obscure bearing on that of any 

 other department of Natural History. Nature — 



" Acts not by partial, but by general laws." 



And these laws can never be fully understood, 

 so long as they are contemplated only partially — so 

 long as any tribe of created beings, and especially 

 so extensive and important a tribe as that under 

 consideration, is excluded from the account. 



