On the Generation of Animals 730a24
"It is clear then from what has been said that, in those animals that emit seed, the seed does not come from every part; and that the female does not contribute in the same way as the male to the generation of the offspring that are constituted, but the male contributes a source of movement and the female the matter. This is why the female does not generate by itself; for it needs a source and something to provide movement and definition (though of course in certain animals, for example hens, nature can generate up to a point; for those do constitute, but the products are unperfected, the so-called wind-eggs)."