Inhaltsangabe
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.1895 Excerpt: ... 1. The embryo can elongate posteriorly without the addition of material from the germ-ring. 2. Under normal conditions a certain amount of material passes from the germ-ring into the embryo. Another interpretation of the results of such an experiment suggested itself early in the work. If one-half of the early two-cell stage may develop a perfect embryo, why may not the embryo cut off from the germ-ring also reproduce the rest of the body on the injured side? An answer was not far to seek. The early stages of development are passed through quite rapidly, and if one-half of the embryo were regenerating it would certainly lag behind the normal half, and the embryo would bend over towards the regenerating side. But a study of the embryo shows that there is very little, if any, delay in the elongation of the embryo. The tail-knob and neuro-notochordal plate elongate symmetrically, and only the mesoderm is unsymmetrically developed. These facts, taken in connection with a study of the normal processes, exclude any interpretation of the phenomenon as involving regeneration. Abnormal Development. Attempts were made to modify the development of the embryo, by placing the developing eggs of Ctenolabrus into artificial media. The addition of more salt to the sea-water (1 to 5 parts to 100 parts sea-water) gave no results of interest. Many embryos developed normally in the more dilute solution (1 part NaCl), but nearly all died in the more concentrated solution (s parts). The eggs had been put into the solutions when the embryo had just appeared. Another lot were placed in the solution when the embryo had reached the equator of the eggs, but the same results followed. The addition of alcohol to the extent of 1 ft to the sea-water, did not seem to seriously affect the ...
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