All quadrupeds, as horses, oxen, &c. which are clothed with hair, and cetaceous fishes, as dolphins and whales, are viviparous; but cartilaginous animals, and vipers, are not truly viviparous, because they produce an egg within themselves before the live animal appears. Oviparous animals are of two kinds, those which produce perfect eggs, as birds, lizards, turtles, &c. and those which produce imperfect eggs, as fishes, whose eggs augment and come to perfection after they have been laid in the water by the female; and in all kinds of oviparous animals, excepting birds, the females are generally larger than the males, as fishes, lizards, &c. After having mentioned these general varieties in animals, Aristotle begins with examining the opinion of the ancient philosophers, that the seed, as well of the male as of the female, proceeded from all parts of the body; he declares against this opinion, because, he says, although children often resemble their fathers and mothers, they also sometimes resemble their grandfathers; and, besides, they resemble their parents by the voice, hair, nails, carriage, and manner of walking. Now the seed, he continues, cannot proceed from the hair, voice, nails, or any external quality, like that of walking; therefore children do not resemble their parents because the seed comes from every part of the body, but for some other reason. It appears to me unnecessary here to point out the weakness of these arguments; I shall only observe that it appears to me this great man expressly sought after methods to separate himself from the sentiments of those philosophers who preceded him; and I am persuaded, that whoever reads his treatise on generation with attention, will discover that a strong design of giving a new system, different from that of the ancients, obliged him always to give the preference to the least probable reasons, and to elude, as much as he could, the force of proofs, when they were contrary to his general principles of philosophy.