Page:The Works of William Harvey (part 1 of 2).djvu/558

 and because the identity is in conformity with reason. For the vegetal primordium which lives potentially is also an ani. mal potentially. Nor can the distinction which Aristotle 1 made between the egg and the worm be admitted : for he de- fines an egg to be that " from part of which an animal is pro- duced ; whilst that," he says elsewhere, 2 " which is totally changed, and which does not produce an animal from a part only, is a worm." These bodies, however, agree in this, that they are both inanimate births, and only animals potentially ; both consequently are eggs.

And then Aristotle himself, whilst he speaks of worms in one place, designates them by the name of eggs in another. 3 Treating of the locust, he says, 4 " its eggs become spoiled in autumn when the season is wet ;" and again, speaking of the grasshopper, he has these words, " when the little worm has grown in the earth it becomes a matrix of grasshoppers (tettigometra) ;" and immediately afterwards, " the females are sweeter after coitus, for then they are full of white eggs."

In this very place, indeed, where he distinguishes between an egg and a worm, he adds: 5 "but the whole of this tribe of worms, when they have come to their full size, are changed in some sort into eggs ; for their shell or covering hardens, and they become motionless for a season, a circumstance that is plainly to be seen in the vermiculi of bees and wasps, and also in caterpillars." Every one indeed may observe that the primordia of spiders, silkworms, and the like, are not less to be accounted eggs than those of the Crustacea and mollusca, and almost all fishes, which are not actually animals, but are potentially possessed of the faculty of producing them. Since, then, those creatures that produce actually are called vivipa- rous, and those that produce potentially either pass without any general distinguishing title or are called oviparous and parti- cularly as such productions are vegetal primordia, analogous to the seeds of plants, which true eggs must needs be held to be, the conclusion is, that all animals are either viviparous or oviparous.

But as there are many species of oviparous animals, so must

1 De Gen. Anim. lib. iii, cap. 9. 4 Hist. Anim. lib. v, cap. 30.

2 Hist. Anim. lib. i, cap. 5. * De Gen. Anim. lib. iii, cap. 9.

3 Ib. lib. v, cap. 29.