upon a fruitful egg ; but not, I believe, in the way in which Aristotle imagines, viz. : that the male concurs in the motion and commencement of generation only, the female supplying nothing but the matter, because the contrary of this is obvious in hype- nemic eggs. And although it be true as he says : " That male and female differ in respect of reason, because the faculty of each is different, and, in respect of sense, because certain parts differ likewise. The difference according to reason boasts this dis- tinction, that the male has the power of engendering in another; the female has only the power of engendering in her- self ; whereby it comes that that which is engendered is pro- duced, this being contained in that which engenders. But as males and females are distinguished by certain faculties and functions, and as an instrument is indispensable to every office, and the parts of the body are adapted as instruments of the functions, it was necessary that certain parts should be set aside for purposes of procreation and coition, and these differing from one another, whereby the male differs from the female/'
It does not, however, follow from thence, that what he ap- pears inclined to infer is correct, where he says : " The male is the efficient agent, and by the motion of his generative virtue (genitura), creates what is intended from the matter contained in the female; for the female always supplies the matter, the male the power of creation, and this it is which constitutes one male, another female. The body and the bulk, therefore, are necessarily supplied by the female ; nothing of the kind is re- quired from the male; for it is not even requisite that the instru- ment, nor the efficient agent itself, be present in the thing that is produced. The body, then, proceeds from the female, the vital principle (anima) from the male ; for the essence of every body is its vital principle (anima)." But an egg, and that animated, is engendered by the pullet without the concur- rence of the male ; whence it appears that the hen too, or the female, may be the efficient agent, and that all creative force or vital power (anima) is not derived exclusively from the male. This view indeed appears to be supported by the instance quoted by Aristotle himself, for he says r 1 " Those animals not of the same species, which copulate, (which those animals do
1 Op. cit. lib. ii, cap. 4.
