tion ; in everything else they agree ; they are both alike pri- mordially vegetables, potentially they are animals. Wherefore, the same theorems and conclusions, though they may appear paradoxical, which we drew from the history of the egg, turn out to be equally true with regard to the generation of animals generally. For it is an admitted fact that all embryos, even those of man, are procreated from some conception or primor- dium. Let us, therefore, say that that which is called pri- mordium among things arising spontaneously, and seed among plants, is an egg among oviparous animals, i. e. a certain cor- poreal substance, from which, through the motions and effi- cacy of an internal principle, a plant or an animal of one description or another is produced; but the prime conception in viviparous animals is of the same precise nature, a fact which we have found approved both by sense and reason.
What we have already affirmed of the egg, viz. that it was the sperma or seed of animals and analogous to the seeds of plants, we now affirm of the conception, which is indeed the seed of an animal, and therefore also properly called ovum or egg. Because " a true seed," according to Aristotle, " is that which derives its origin from the intercourse of male and female, and possesses the virtues of both ; such as is the seed of all vege- tables, and of some animals, in which the sexes are not distinct, and is, as that which is first mingled from male and female, a kind of promiscuous conception or animal ; for it has those things already that are recognised of both ;" i. e. matter adapted to nourish the foetus, and a plastic or formative and effective virtue. And so in like manner is a conception the fruit of the intercourse of male and female, and the seed of the future embryo ; it therefore does not differ from an egg.
" But that which proceeds from the generant is the cause which first obtain^ the principle of generation, (i. e. it is the efficient cause,) and ought to be called the geniture," 2 not the seed, as is commonly done both by the vulgar and philoso- phers at the present time ; because it has not that which is re- quired of both the concurring agents, neither is it analogous to the seeds of plants. But whatever possesses this, and corre- sponds to the seeds of vegetables, that too is rightly entitled egg and conception.
1 De Gen. Anim. lib. 1, cap. 18. " Ibid.
