AIDS AFFORDED BY ANATOMY. 171 



born of the same race, and of the same country. 

 If we look to the animal world, the same results are 

 apparent, more especially in all the leading systems 

 on the vertebrated classes. In ornithology, par- 

 ticularly, there is not a single division which has 

 been mainly founded upon internal structure : so 

 that, in this class, even the Regne Animal follows 

 precisely the plan of the Systema Naturce. Hence 

 we may conclude that external characters are almost 

 always preferable to those founded solely upon in- 

 ternal structure ; and that this conclusion is tacitly 

 admitted by those who, in theory, maintain a contrary 

 opinion. 



(114.) Nevertheless, it would be absurd to sup- 

 pose that the internal construction of an animal is 

 not deserving of great attention. This study, in 

 fact, constitutes, of itself, a distinct branch of phy- 

 sical science ; useful, indeed, to the zoologist, as the 

 means of assisting and guiding his studies, but by 

 no means so essential as is generally supposed. 

 Wherever external peculiarities are sufficient to 

 supply us with clear definitions, we require no other. 

 It must nevertheless be remembered, that when we 

 descend to the lower groups of animal life, where 

 the forms become proportionally simple, we must 

 then have frequent recourse to dissection; not so 

 much, indeed, for the purpose of characterising such 

 forms, as for that of ascertaining to which of the 

 grand divisions of the animal kingdom they truly 

 belong. We allude more particularly to those soft 

 molluscous-like animals, confusedly put into the 

 Linnaean class of Worms. These stand so low in the 

 scale of creation, that many of them have the aspect 



