GEXERATION OF ANIMALS, I. xvin. 



drawn from the various parts of the parent has no 

 right to the same name " as those parts — we may not 

 call that " blood " which is drawn from the parents' 

 blood, and the same ^^ith flesh. This means that the 

 offspring's blood is formed out of something which is 

 other than blood, and if so, then the cause of its 

 resemblance will not be due to the semen's being 

 drawn from all the parts of the parent's body, as the 

 supporters of this theor}' assert — because if blood is 

 formed from something that is not blood,* the semen 

 need only be drawn from one part, there being no 

 reason why all the other constituents as well as blood 

 should not be formed out of the one substance. This 

 theory seems to be identical ^yiih that of Anaxagoras,'^ 

 in asserting that none of the uniform substances 

 comes into being ; the only difference is that whereas 

 he applied the theor}' universally, these people apply 

 it to the generation of animals. Again, how are 

 these parts which were drawn from the whole of the 

 parent's body going to grow ? Anaxagoras gives a 

 reasonable answer ; he says that the flesh alreadv 

 present is joined by flesh that comes from the nourish- 

 ment. Those people however, who do not follow 

 Anaxagoras in the statement just quoted, yet hold 

 that the semen is drawn from the whole bodv, are 

 faced with this question : how is the embrvo to grow 

 bigger bj' the addition of different substance to it 



which the embryo takes in afterwards also contains these 

 substances. Hence the theory gets into a difficulty when the 

 question arises of how the growth of the embrjo is effected. 

 This difficulty is avoided by Anaxagoras, because he makes 

 his principle " a portion of every element in every thing " 

 apply nniversally, and does not limit its application to the 

 semen onlv. (For Anax., see A. L. Peck, C'. XXV { 1931 ), 

 27 ff., 112" if.) 



63 



