to doubt how the semen, which is nowhere to be detected, which is neither mixed with the 'geniture* of the female, nor yet is added to it, nor touches it, can fecundate the egg, or constitute the chick. And this all the more urgently, when he has stated that a few connections in the beginning of the season suffice to secure the fecundity of all the eggs that will be laid in its course. For how should it seem otherwise than impossible that from the semen galli communicated in the spring, but now long vanished, lost or consumed, the eggs that continue to be laid through the summer and autumn, should still be rendered fruitful and fit to produce pullets ?
It is that he may meet such a difficulty half way, that he coins the difference which has been noticed. By way of bol- stering up his views, he farther adduces three additional con- siderations : First, since the semen galli is neither extant in the egg, nor was ever present in the uterus, nor is added as e material cause ' as in viviparous animals, he has chosen to make it resident for a whole year in the body of the hen. And then that he may have a fit receptacle or storehouse for the fecundating fluid, he finds a blind sac near the inlet to the uterus, in which he says the cock deposits his semen, wherein, as in a treasury, it is stored, and from which all the eggs are fecundated. Lastly, although the semen in that bursa comes into contact neither with the uterus, nor the egg, nor the ovary, whereby it might fecundate the egg, or secure the generation of a chick, he says, nevertheless, that from thence, a certain spiritual substance or irradiation penetrates to the egg, fecundates its chalazse, and from these produces a chick. By this affirmation, however, he appears to support the opinion of Aristotle, namely, that the female supplies the ' matter ' in generation, the male the ' efficient force ;' and to oppose the postulate of medical writers about the mixture of seminal fluids, for the sake of which, never- theless, as I have said, he seems to have laid down his dis- tinction between oviparous and viviparous animals. To give an air of greater likelihood to this notion of his, he goes on to enumerate the changes which the semen, not yet emitted, but laid up in the testes and vesiculae seminales of animals, oc- casions.
But besides the fact that all this does not bear upon the
