290 ON GENERATION. 



tive of ei'fpytiq. or efficiency. For is not that to be accounted 

 efficient in which the reason of the embryo and the form of the 

 work appear ; whose obvious resemblance is perceived in the em- 

 bryo, and which, as first existing, calls forth the other ? Since, 

 therefore, the form, cause, and similitude inhere in the female 

 not less and it might even be said that they inhere more 

 than in the male, and as she also exists previously as prime 

 mover, let us conclude for certain that the female is equally 

 efficient in the work of generation as the male. 



And although Aristotle* says well and truly, "that the concep- 

 tion or egg receives no part of its body from the male, but only 

 its form, species, and vital endowment (anima), and from the 

 female its body solely, and its dimensions," it is not yet made 

 sufficiently to appear that the female, besides the matter, does 

 not in some measure contribute form, species, and vital endow- 

 ment (anima). This indeed is obvious in the hen which en- 

 genders eggs without the concurrence of a male ; in the same 

 way as trees and herbs, in which there is no distinction of sexes, 

 produce their seeds. For Aristotle himself admits, 2 that even 

 the hypenemic egg is endowed with a vital principle (anima). 

 The female must therefore be esteemed the efficient cause of the 



egg- 

 Admitting that the hypenemic egg is possessed of a certain 

 vital principle, still it is not prolific ; so that it must further 

 be confessed that the hen of herself is not the efficient cause of 

 a perfect egg, but that she is made so in virtue of an authority, 

 if I may use the word, or power required of the cock. For the 

 egg, unless prolific, can with no kind of propriety be accounted 

 perfect; it only obtains perfection from the male, or rather 

 from the female, as it were upon precept from the male ; as if 

 the hen received the art and reason, the form and laws of the 

 future embryo from his address. And so in like manner the 

 female fowl, like to a fruitful tree, is made fertile by coition ; by 

 this is she empowered not only to lay eggs, but these perfect and 

 prolific eggs. For although the hen have as yet no rudiments of 

 eggs prepared in her ovary, nevertheless, made fertile by the 

 intercourse of the male, she by and by not only produces them 

 there, but lays them, teeming with life, and apt to produce 



1 Op. cit. lib. ii, cap. 4. Ibid. 



