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 foetus 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.