GENERATION OF ANIMALS, I. i. 



lo be swimmers, or fliers, or walkers, male and female 

 are found ; and this applies not only to the blooded 

 animals but to some of the bloodless ones as well. 

 And among the latter, in some cases it holds good of 

 a whole group, as for instance the Cephalopods and 

 the Crustacea " ; and it holds good of most of the 

 Insects. Among animals of this class, those which 

 are formed as the result of the copulation of animals 

 of the same kind, themselves generate in turn after 

 their o^vn kind ; those, however, which arise not 

 from h\-ing animals but from putrescent matter, 

 although they generate, produce something that is 

 different in kind, and the product is neither male nor 

 female. Some of the Insects are Uke this.** And 

 this is what we should expect ; for supposing that 

 creatures which are produced other^^ise than from 

 Uving animals copulated and produced Uving animals : 

 if these products were similar in kind to their parents, 

 then the manner of their parents' original generation 

 should have been like theirs. This we may reason- 

 ably claim, because it is e\ident that this is so \rith 

 all other animals. If, on the other hand, the pro- 

 ducts were dissimilar from their parents, and yet able 

 to copulate, we should then get arising from them 

 yet another different manner of creature, and out of 

 their progeny yet another, and so it would go on ad 

 infimtum. Nature, however, avoids what is infinite, 

 because the infinite lacks completion and finality, 

 whereas this is what Nature always seeks, (b) The 

 creatures which cannot move about, Uke the Tes- 

 tacea and those which live by being attached to some 

 surface, are in their essence similar to plants, and 

 therefore, as in plants, so also in them, male and 



* See 732 a 25 ff., 758 b 6 ff. 



