and these eggs, although perfect, are unfruitful: he does not agree with the opinion of country people, that two or three days cohabitation with the cock is sufficient to impregnate all the eggs a hen will lay within the year, but admits that he separated a hen from a cock for the space of twenty days, and that all the eggs she laid during that space were fecundated. While the egg is fastened to the ovarium, it derives its nutriment from the vessel of the common pellicle. But as soon as it is loosened from it, it derives the white liquor which fills the passages in which it descends, and the whole, even to the shell, is formed by this mode.

The two ligaments (chalazæ) which Aquapendente looks on as the shoot produced by the seed of the male, are found in the infecund eggs which the hen produces without the communication with the cock, as in those which are impregnated: and Harvey very judiciously remarks, that those parts do not proceed from the male, and are not those which are fecundated; the fecundated part of an egg is a very small white circle which is on the membrane that covers the yolk, and forms there a small spot, like a cicatrice, about the size of a lentil. Harvey also remarks, that this little cicatrice is found in every fecund or infecund egg, and that those who think it is produced by the seed of the male are deceived. It is of the same size and form in fresh eggs, as in those which have been kept a long time; but when we would hatch them, and when the egg receives a sufficient degree of heat, either by the hen, or artificially, we presently see this small spot increase and dilate nearly like the sight of the eye. This is the first change, and is visible at the end of a few hours incubation.

When the egg has undergone a proper warmth for twenty-four hours, the yolk, which was before in the centre of the shell, approaches nearer to the cavity at the broad end; this cavity is increased by the evaporation of the watery part of the white, and the grosser part sinks to the small end. The cicatrice, or speck, on the membrane of the yolk, rises with it to the broad end, and seems to adhere to the membrane there: this speck is then about the bigness of a small pea, in the middle of it a white speck is discernible, and many circles, of which this point seems to form the centre.

At the end of the second day these circles are larger and more visible; the streak also appears divided by these circles into two, and sometimes three parts of different colours; a small protuberance also appears on the external part, and nearly resembles a small eye, in the pupil of which there is a point, or little cataract; between these circles a clear liquor is contained by a very delicate membrane, and the speck now appears more to be placed in the white than on the membrane of the yolk. On the third day the transparent liquor is considerably increased, as is also the small membrane which surrounds it. The fourth day, a small streak of purple-coloured blood is observed at the circumference of the speck or ball, at a little distance from the centre of which a point may be seen of a blood colour, and which beats like a heart. It appears like a small spark at each diastole, and disappears at each systole; from this animated speck issue two small blood vessels, which these small vessels throw out as branches into this liquor, all of which come from the same point, nearly in like manner as the roots of a tree shoot from the trunk.

Towards the end of the fourth day, or at the beginning of the fifth, the animated speck is so much increased as to appear like a small bladder filled with blood, and by its contractions and dilations is alternatively filled and emptied. In the same day this vessel very distinctly appears to divide into two parts, each of which alternatively impel and dilute the blood in the same manner. Around the shortest sanguinary vessel which we have spoken of a kind of cloud is seen, which, although transparent, renders the sight of this vessel more obscure; this cloud constantly grows thicker and more attached to the root of the blood vessel, and appears like a small globe: this small globe lengthens and divides into three parts, one of which is globular, and larger than the other two; the head and eyes now begin to appear, and at the end of the fifth day, the place for the vertebra is seen in the remainder part of this globe.

The sixth day the head is seen more clearly, the outlines of the eyes now appear, the wings and thighs lengthen, and the liver, lungs, and beak, are distinctly observed; the fœtus now begins to move and extend its head, although it has as yet only the internal viscera; for the thorax, abdomen, and all the external coverings of the fore part, of the body are wanting. At the end of this day, or at the beginning of the seventh, the toes appear, the chick opens and moves its beak, and the anterior parts of the body begin to cover the viscera; on the seventh day the chicken is entirely formed, and from this time until it comes out of the egg, nothing happens but only an expansion of those parts it acquired within these first seven days: at the fourteenth or fifteenth day the feathers appear, and at the twenty-first it breaks the shell with its beak, and procures its enlargement.

These observations of Harvey appear to have been made with the greatest exactness; nevertheless we shall point out how imperfect they are, and that he has fallen himself into the error he reproaches others with, making experiments to support his favourite hypothesis, that the heart was the animated speck which first appeared; but before we proceed on this matter, it is but just to give an account of his other observations, and of his system.

It is well known that Harvey made many experiments on hinds and does. They receive the male towards the middle of September: a few days after copulation the horns of the matrix become thicker, and at the same time more lax. In each of the cavities five carunculas appear. Towards the 26th or 28th of the above month the matrix thickens still more, and the five carunculas are swelled nearly to the shape and size of a nurse's nipple; by opening them, an infinity of small white specks are found. Harvey pretends to have remarked, that there was neither then, nor immediately after copulation, any alteration or change in the ovarium, and that he has never been able to find a single drop of the seed of the male in the matrix, although he has made many researches for that purpose.

Towards the end of October, or beginning of November, when the females separate from the males, the thickness of the horns begins to diminish, the internal surfaces of their cavities are swelled, and appear fastened together; the carunculas remain, and the whole, which resembles the substance of the brain, is so soft that it cannot be touched. Towards the 13th or 14th of November, Harvey says, that he perceived filaments, like the threads of a spider's web, which traversed the cavities of the horns and the matrix itself: these filaments shoot out from the superior angle of the matrix, and by their multiplication form a kind of membrane, or empty tunic; a day or two after this tunic is filled with a white, aqueous and glutinous matter, which adheres to the matrix by a kind of mucilage; and in the third month this tunic, or pouch, contains an embryo about the breadth of two fingers long, and another internal pouch, called the amnios, containing a transparent crystalline liquor, in which the fœtus swims. The fœtus at first was but an animated speck, like that in the egg of a fowl. All the rest is performed in the same manner as that related of the chick; the only difference is