PARTS OF ANIMALS, I. iii. 



number, or some higher value of 2" ; and there will 

 be an identical number of species." 



(The species is the differentia in the Matter. There 

 is no animal part which exists without matter ; nor 

 on the other hand is there any which is matter only, 

 for body in any and every condition cannot make an 

 animal or any part of an animal, as I have often 

 pointed out.^) 



(e) Again, the division ought to be made according 

 to points that belong to the Essence of a thing and 

 not according to its essential (inseparable) attributes. 

 For instance, in making divisions of geometrical 

 figures, it would be wrong to di\dde them into those 

 whose angles are together equal to two right angles 

 and those whose angles are together greater than two 

 right angles ; because it is only an attribute of the 

 triangle that its angles are together equal to two 

 right angles.'' 



(f) Again, division should be by " opposites," 

 opposites being mutually " different," e.g. pale and 

 dark, straight and curved. Therefore, provided the 

 two terms are truly " different," di\ision should be 

 by means of opposites, and should not characterize 

 one side by ability to s\\'im and the other side by 

 some colour. And besides this, division of li\dng 

 creatures, at any rate, by the functions which are 

 common functions of body and soul,*^ such as we 

 actually find done in the divisions mentioned above, 

 where animals are divided into " walkers " and 

 " fliers " — for there are some groups, such as that of 

 the Ants, which have both attributes, being both 



locomotive, and thought (see De an. 414 a 28 ff.). His point 

 is that the correct way to divide and classify animals is rather 

 by bodily characteristics, which is what he himself does. 



sr 



