This famous anatomist, to whom we are indebted for the discovery of the circulation of the blood, has composed a very extensive treatise on generation; he lived towards the middle of the last century, and was physician to Charles I. of England. As he was obliged to follow this unfortunate prince in his misfortunes, he lost what he had written on the generation of insects among other papers, and he composed what he has left us on the generation of birds and quadrupeds from his memory. I shall concisely relate his observations, his experiments, and his system. Harvey asserts that man and every animal proceed from an egg; that the first produce of conception in viviparous animals is a kind of an egg, and that the only difference between viviparous and oviparous is, that the foetus of the first take their origin, acquire their growth, and arrive at their entire expansion in the matrix; whereas the foetus of oviparous animals begins to exist in the body of the mother, where they are merely as eggs, and it is only after they have quitted the body of the mother that they really become foetuses; and we must remark, says he, that in oviparous animals, some hold their eggs within themselves till they are perfect, as birds, serpents and oviparous quadrupeds; others lay their eggs before they are perfect, as fish, crustaceous, and testaceous animals. The eggs which these animals deposit are only the rudiments of real eggs, they afterwards acquire bulk and membranes, and attract nourishment from the matter which surrounds them. It is the same, adds he, with insects, for example, and caterpillars, which only seem imperfect eggs, which seek their nutriment, and at the end of a certain time arrive to the state of chrysalis, which is a perfect egg. There is another difference in oviparous animals: for fowls and other birds have eggs of different sizes, whereas fish, frogs, &c. lay them before they are perfect, have them all of the same size; he indeed observes, that in pigeons, who only lay two eggs, all the small eggs which remain in the ovarium are of the same size, and it is only the foremost two which are bigger than the rest. It is the same, he says, in cartilaginous fish, as in the thornback, who have only two eggs which increase and come to maturity, while those which remain in the ovarium are, like those in fowls, of different sizes. He afterwards makes us an anatomical exposition of the parts necessary to generation, and observes, that in all birds the situation of the anus and vulra are contrary to the situation of those parts in other animals; the anus being placed before and the vulra behind;[D] and with respect to the cock, and all small birds, that they generate by external friction, having in fact no intermission nor real copulation; with male ducks, geese, and ostriches, it is evidently otherwise. [D] Most of these articles are taken from Aristotle.