BOOK IV 



The formation of animals, both in general and as con- I 

 cems all of them separately, has now been dealt vrith. ^^n-"'. 

 Since, however, in the most perfect " of them the entiation. 

 male and the female are separate, and we hold that theories: 

 these characteristics ^ are " principles " "^ of all animals 

 and all plants ahke (the only difference being that in 

 some these " principles " are inseparable while in 

 others they are separate), we must deal with the 

 formation of these first of all, for male and female 

 become distinct while animals are still imperfect 

 in kind.*^ It is however not agreed whether one is 

 male and another female even before the difference 

 is plain to our senses, the difference being acquired 

 by them either within the mother or earUer. Thus, Anaxagoras. 

 some people, such as Anaxagoras and certain other 

 physiologers,'' say that this opposition exists right 

 back in the semens,^ alleging that the semen comes 



Aristotle's view will be found in the passage below, 766 a 30- 

 b 3. The heart is the first thing to be formed in the embryo, 

 because it is the seat of to dpeirriKov, the nutritive part of the 

 Soul; and to BpermKov is also ro yewrjriKov (see 735 a 17 fF., 

 744 b 36, n.). Sex can be ultimately traced back to the 

 heart, which, as also containing the principle of vital heat, 

 is the source of concoction, upon which ability to produce 

 semen, etc., depends. 



• See pp. xvi f. 



^ This is an example of the view that the diflFerence is 

 acquired " earlier " than in the mother. 



371 



