GENERATION OF ANIMALS, II. iv. 



after all it is not true to say that all the nourishment 

 comes from outside. In the seeds of plants there is 

 some nutritive matter, which at first has a milky 

 appearance ; and it may be that in the same way, 

 in the material of the animal, the residue left over 

 from its construction is present as nourishment for it 

 from the outset. 



So then, the fetation's gro^vth is supplied through 

 the umbilicus in the same way that a plant's growth 

 is supplied through its roots [and also as that of 

 animals is, when they have been separated, from 

 the nourishment which is in themselves]." Of these 

 matters we shall have to speak later at the appropriate 

 occasions in our discussions. As for the ditferentia- 

 tion of the various parts : this is not due, as some 

 suppose, to any natural law that " Uke makes its way 

 to Uke." * This theory involves quite a number of 

 difficulties, one being that if you accept it as stating 

 a valid reason, it follows that each of the " uniform " 

 parts, such as bones, and sinews, and flesh, is formed 

 separately, each one all on its own. The true reason 

 why each of these parts is formed is that the residue 

 provided by the female is potentially the same in 

 character as the future animal will be, according to 

 its nature : and although none of the parts is present 

 in actuality in that residue, they are all there potenti- 

 ally. A further reason is this. When a pair of 

 factors, the one active and the other passive, come 

 into contact in the way in which one is active and the 

 other passive (by " way " I mean the manner, the 

 place, and the time of the contact), then immediately 

 both are brought into play, the one acting, the other 

 being acted upon. In this case, it is the female which 

 provides the matter, and the male which provides the 



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