GENERATION OF ANIMALS, I. xviii. 



unless the substance that is added changes ? If how- 

 ever it is admitted that this added substance can 

 change, why not admit straight away that the semen 

 at the outset is such that out of it blood and flesh can 

 be formed, instead of maintaining that the semen is 

 itself both blood and flesh ? They might try to argue 

 that it grows at a later stage by admixture, just as 

 wine is increased in bulk by pouring in water ; but 

 even this line of argmnent proves impossible, because 

 if that were so, then it would surely be at the outset 

 that each of the parts was its own proper self, before 

 it was mixed, whereas in actual fact it is at a later 

 stage that this occurs (I refer of course to flesh and 

 bone and every one of the rest of them). And the 

 assertion that some of the semen is sinew and bone 

 is quite beyond us, as the saying goes. 



Here is another objection. Suppose it is true that 

 the differentiation between male and female takes 

 place during conception, as Empedocles says " : 



Into clean vessels were they poured forth ; 

 Some spring up to be women, if so be 

 They meet with cold. . . . 



Anyway, both men and women are observed to 

 change : not only do the infertile become fertile, 

 but also those who have borne females bear males ; 

 which suggests that the cause is not that the semen 

 is or is not drawn from the whole of the parents, but 

 depends upon whether or not that which is drawn 

 from the man and from the woman stand in the right 

 proportional relation to each other.'' Or else it is 

 due to some other cause of this sort. Thus, if we are 

 to assume this as true, viz., that the same semen is 



» C/. 767 a 16, 773 a 17, and Introd. § 39. 



D 65 



