GENERATION OF ANIMALS, III. vii. 



In birds, wind-eggs become fertile," and eggs Wind-eg 

 previously impregnated by the treading of one sort 

 of cock clxange their nature to that of the cock which 

 treads the hen later ^ : and also, where one and the 

 same cock is concerned,*' if he has left off treading 

 the hen and the eggs are not growing on that 

 account, he makes them grow quickly when he re- 

 sumes the treu-ling. This however cannot happen 

 at any and every period ; the treading must take 

 place before the change occurs when the white of the 

 Ggg becomes separate. In the case of fishes' eggs 

 there is no such point fixed, but the males sprinkle 

 *hem without delay to keep them in sound condi- 

 tion. The reason is that fishes' eggs are not double- 

 coloured : that is why in their case there is no such 

 fixed time as there is for birds' eggs. This situation 

 is what we should expect, for once the white and the 

 yolk have been distinctly separated from each other, 

 they already '^ possess the principle that comes from 

 the male,* since the male contributes [towards] this. 

 Thus wind-eggs attain to generation in so far as it 

 is possible for them to do so. It is impossible for 

 them to be perfected to the point of producing an 

 animal, because sense-perception ^ is required for 

 that ; the nutritive faculty of the Soul, however, is 

 possessed by females as well as by males and by all 



" Probably there should here be inserted " if the hen is 

 trodden by the male while they are in the uterus." 



* This is qualified below, 757 b 27 fF. 



' The force of oiKela seems to be that the eggs are the 

 cock's " own " in the sense that he and not some other cock 

 originally impregnated them. But see critical note. 



'* And therefore cannot be altered by another cock. 



' See 767 b 17 ff., and references there given in note. 



' Which is supplied by the male. 



M 321 



