The mature Ovum of Myxine.—The earliest description of the mature ovum is that given by Allen Thomson, in the article “Ovum” in Todd's Cyclopædia of Anatomy and Physiology, vol. v., published in the year 1859. He says:—“I have found that in the Myxine glutinosa the globular yolk is enclosed in a horny capsule of similar consistence and structure (to that of Elasmobranchs), but of a simple elongated ellipsoidal shape; and in place of four terminal angular tubes there are a number of trumpet-shaped tubular processes projecting from the middle of the two ends, which probably serve the same purpose as the differently shaped appendages of the ova of the shark and skate.” He gives a figure in woodcut of the ovum, and of one of the threads magnified. The figures are correct with this exception: in the representation of the entire ovum the yolk is represented in outline as though seen through the envelope, and is globular, like the yolk of Elasmobranchs. In the Myxine ovum the yolk fills the cavity of the ellipsoidal envelope. It is not true that the terminal processes are tubular. I have examined them, and found them solid, and, as far as can be seen with a low power, homogeneous. I have not been able to ascertain from what specimen or specimens the description of Thomson is taken, but there is a single specimen of the ripe ovum in Professor Turner's museum which may have been examined by Thomson. This specimen was brought to the museum in the time of Professor Goodsir, but it is not possible now to ascertain whether it was dredged from the sea-bottom or taken from a pregnant female.