GENERATION OF ANIMALS, I. xx. 



is required in order to produce numerous offspring is 

 that there should be the right amount of it to suit 

 the material available — neither so little that it fails 

 to concoct it or even to set it, nor so much that it 

 dries it up." If on the other hand this semen which 

 causes the original setting remains single and un- 

 divided, then one single offspring only is formed 

 from it. 



The foreffoinor discussion will have made it clear 

 that the female, though it does not contribute any 

 semen to generation, yet contributes something, viz., 

 the substance constituting the menstrual fluid (or the 

 corresponding substance in bloodless animals). But 

 the same is apparent if we consider the matter gener- 

 ally, from the theoretical standpoint. Thus : there 

 must be that which generates, and that out of which 

 it generates ; and even if these two be united in 

 one,'' at any rate they must differ in kind,*^ and in 

 that the logos "^ of each of them is distinct. In those 

 animals in which these two faculties are separate, 

 the body- — that is to say the physical nature — of the 

 active partner and of the passive must be different. 

 Thus, if the male is the active partner, the one which 

 originates the movement, and the female qua female 

 is the passive one, surely what the female contributes 

 to the semen of the male ^\ill be not semen but 

 material. And this is in fact what we find happen- 

 ing ; for the natural substance of the menstrual fluid 

 is to be classed as " prime matter." * 



KtvTqaecas koI /lerajSoA^s." In its lowest phase, " prime matter" 

 is that which, united with the prime contrarieties (hot, cold, 

 solid, fluid), produces the " elements " Earth, Air, Fire, 

 Water; but, as the term "prime " itself suggests, " matter" 

 is altogether a relative conception, and in its highest phase 

 matter is one and the same as "' form " {Met. 1045 b 18). 



Ill 



