o6 INTRODUCTION. 



existing, in a still more marked decree, between 

 the various other organs of each, how well cal- 

 culated must be the study of the one, to illustrate 

 the nature of the other ! Nature acknowledges no 

 sudden transitions — she has made no animated being 

 isolated — none w^hich is not connected by one link 

 below, and by another above itself, with all the 

 )est — man alone, in this particular, excepted. 

 And while she has constructed no hnks but what 

 constitute a part of the great chain, extending from 

 the lowest animated being up to man, she has left 

 no gap in tliis chain into which one additional link 

 could have been advantageously inserted. And 

 who shall say that the Divine hand, which has 

 permitted man to be elevated so much higher than 

 other animals upon the same foundation, has not 

 permitted other beings to proceed infinitely further 

 still ; so that to them man is far, far more insigni- 

 ficant and contemptible, than to him is the veriest 

 worm that crawls. Can we, then, for a moment 

 imagine, that a knowledge of the structure of so 

 extensive a tribe as that of fishes, the connecting 

 series of links, as it were, betAveen the two funda- 

 mental divisions of the whole animal kingdom, the 

 vertebrated and avertebrated, is isolated, and cal- 

 culated to throw no light upon that of other ani- 

 mals; or that we can perfectly understand the 

 economy of any one tribe, so long as we remain 

 ignorant of the numberless points of analogy w^hich 

 this interesting tribe presents in relation to every 

 other ? And, with respect to the functions and 



