PARTS OF ANIMALS, I. iv.-v. 



Birds, Fishes, Cephalopods," Testacea.^ Within each 

 of these groups, the parts do not differ so far that they 

 correspond only by analogy (as a man's bone and a 

 fish's spine) ; that is, they differ not structurally, but 

 only in respect of bodily quahties, e.g. by being 

 larger or smaller, softer or harder, smoother or 

 rougher, and so forth, or, to put it generally, they 

 differ " by the more and less." 

 We have ηοΛν shown : 



(1) how to test a method of Natural science ; 



(2) what is the most systematic and easiest way of 

 studying Natural science ; 



(3) Λvhat is the most useful mode of Division for 

 our present purpose ; 



(4) why dichotomy is in one respect impossible and in 

 another futile. 



Now that we have made this beginning, and clearly 

 distinguished these points, we may proceed. 



V. Of the works of Nature there are, we hold, two Aprotreptic 

 kinds : those which are brought into being and perish, of anhnalsf^ 

 and those which are free from these processes through- 

 out all ages. The latter are of the highest worth and 

 are divine, but our opportunities for the study of 

 them are someΛvhat scanty, since there is but little 

 evidence available to our senses to enable us to con- 

 sider them and all the things that we long to knoΛv 

 about. We have bettermeans of information, however, 

 concerning the things that perish, that is to say, plants 

 and animals, because Λve live among them ; and any- 

 one who will but take enough trouble can learn 

 much concerning every one of their kinds. Yet 

 each of the two groups has its attractiveness. For 

 although our grasp of the eternal things is but 

 slight, nevertheless the joy which it brings is, by 



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