Memoirs (Volume 7) (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915. Excerpt: ... sixteen days old, the normal embryo hatches and becomes free swimming at about twelve days. As mentioned above, a similar series of normal embryos have been prepared and used for comparison with these non-circulating individuals. In order to be certain of the final developmental product of the blood cells of the fish, numerous smears have been made from various tissues and from heart blood taken from the adult Fundulus. In these smears one finds the various types of white blood cells and the ordinary red blood corpuscles of Teleosts. THE STUDY OF LIVING EMBRYOS WITH AND WITHOUT THE CIRCULATION OF THE BLOOD /. Normal development up to the establishment of a circulation The rate of development of Fundulus embryos is very variable, differing at different periods of the breeding season, and also differing in groups of eggs from different individuals. When twenty-four hours old, the germ ring has descended almost to the equator in the most rapidly developing individuals. In others the ring is only one-third way over the yolk sphere. The embryonic shield and the first line indicating the position of the embryo's body is now to be made out. At forty-eight hours, the yolk sphere is completely covered by the ectoderm, the embryonic body is well shown with the optic knobs projecting prominently and several somites easily distinguishable. The heart has not begun to pulsate and no blood cells or blood anlage are distinguishable in the living specimen. Very soon after this time, or at least by sixty-eight hours, there are about ten somites present and collections of cells on the yolk-sac are the first indication of blood islands. No pigment cells have formed up to sixty hours. At seventy-one hours pigment cells are recognizable but the blood islands are not yet colore...