may be remarked. The spinal marrow, divided into two parts, is extended along the trunk; the liver, previously whitish, becomes of a darker dusky colour. It is now seven lines* in length.

An Egg as it appears six days after incubation, with a magnified view of the Chick.

On the seventh day it is easy to distinguish the bill; and the skin, with the germs of the feathers, becomes obvious.

On the eighth day the brain, the wings, thighs, and legs, have taken nearly their ultimate form; but, according to Scarpa, are still soft, flexible, and pellucid t. The two ventricles of the heart also appear like two bubbles, contiguous and joined above to the substance of the auricles; while two successive motions are now observed in them, as well as in the auricles, which resemble two separate hearts.

* A line is the twelfth part of a French, or rather less than the eleventh of an English inch.

De Penit, Ossium Structura Comment. 4to. Lips. 1799.

of the Chick.

An Egg as it appears nine days after incubation.

On the ninth day the bones begin to be formed, appearing in the form of hard bony joints, the middle of the thigh and leg-bones, according to Scarpa, becoming yellowish. These form the rudiments of the bony ring of the sclerotic, resembling a circular row of the most delicate pearls. At the same period the marks of the beautiful yellow vessels on the yolkbag begin to be visible.

On the tenth day the muscles of the wings are seen completely formed, and the germs of the feathers appear enlarging. Scarpa up to this period could observe nothing hard, but a yellow wrinkling of beautiful network*.

An Egg as it appears ten days after incubation. On the eleventh day the arteries begin to be distinct, those which were previously at a distance from the heart now joining and cohering to it. It

The Embryo Chick taken from the preceding Egg, with the amnion and vesicle removed.

was now that Scarpa first observed the wrinkles in the leg and thigh-bones to become rough and hard, and red spots to appear.

On the twelfth or thirteenth day, if the membrane (chorion) enveloping the white of the egg be examined by very cautiously opening the shell, it will present, Blumenbach says, without any artificial injection, one of the most splendid spectacles that occurs in the whole organic creation,-the most simple, yet the most perfect substitute for the lungs. It exhibits a surface covered with countless bloodvessels, venous and arterial, branching through its texture. The veins are of a bright scarlet colour, carrying oxygenated blood to the chick; while the arteries, on the other hand, are of a deep crimson or livid red, bringing the carbonated blood from the body of the embryo. The functions of the two are thus the reverse of those they perform after the chick respires. From the trunks of these arteries being connected with the iliac vessels, and on account of

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