GENERATION OF ANIMALS, 11. i. 



they all grow in size after they have been produced), 

 and these young which they generate are hving 

 creatures inside them from the outset. (2) The 

 second class do not generate perfect animals within 

 themselves from the outset : although they are vivi- 

 parous, they lay eggs first of all ; externally however 

 they are viviparous. (3) Others produce not a per- 

 fect animal, but an egg, which is perfect. (4) Those 

 whose constitution is still colder than this produce 

 an egg, but it is not a perfect one : it reaches its per- 

 fection outside the parent. Examples are the scaly 

 fishes, the Crustacea and the Cephalopods. (5) The 

 fifth class of creatures, which are the coldest of all, 

 do not even lay an egg directly themselves, but the 

 formation of their egg takes place outside the parent, 

 as has been said." What happens is that Insects 

 first produce a larva, then the larva develops till it 

 becomes egg-hke (what is called the chrysalis is really 

 equivalent to an egg ^) ; then out of this an animal 

 is formed, and it is not until this third stage in its 

 series of changes that it reaches the end and perfec- 

 tion of its generation. 



There are, then, some animals which are not formed 

 from semen, as I have in fact said already. All 

 blooded ones, however, are formed from semen, so 

 many as are formed as the result of copulation, that 

 is to say, the male emits semen into the female, 

 and upon the entry of the semen the young animals 

 are " set " and constituted and assume their proper 

 shape ; with the xiviparous animals this stage takes 

 place within the parent, with others in the eggs [and 

 seeds and other such secretions]. 



And on this subject we are confronted by no small How utiie 

 " Lit., " has the dynamis of an egg " : see Introd. § 2Q. 



143 



