. Biological lectures delivered at the Marine Biological Laboratory of Wood's Holl [sic]. Biology. OA PH YSIOL OGICA L MORFHOL OG J \ 51 grown together. Of course, it often happened that, by accident or rapid movement, the twins were separated, and they then developed into perfectly normal single embryos. Since we cannot assume that in every case the same part of the protoplasm escapes, we must conclude that every part of the protoplasm may give rise to fully developed embryos without regard to preformed germ-regions. In many eggs a. Fig. 15. repeated outflow of the proto- plasm takes place (F
. Biological lectures delivered at the Marine Biological Laboratory of Wood's Holl [sic]. Biology. OA PH YSIOL OGICA L MORFHOL OG J \ 51 grown together. Of course, it often happened that, by accident or rapid movement, the twins were separated, and they then developed into perfectly normal single embryos. Since we cannot assume that in every case the same part of the protoplasm escapes, we must conclude that every part of the protoplasm may give rise to fully developed embryos without regard to preformed germ-regions. In many eggs a. Fig. 15. repeated outflow of the proto- plasm takes place (Fig. 15). In such cases each of the drops of the protoplasm may give rise to an embryo, and I obtained not only double embryos, but triplets and quadruplets all grown together. In order to understand these experiments more fully, let us follow out the history of development in these double and multiple monstrosities. The ova were put into the diluted sea-water before any segmentation had taken place and while they had still but one nucleus. When parts of the protoplasm flowed out, the nucleus either remained in the protoplasm, inside of the membrane, or passed out with the part that was ejected. Therefore, at first, only one part of the protoplasm contained a nucleus. The other part obtained its nucleus by the cleavage which took place, as follows : In case the nucleus had remained inside the membrane (Fig. 16), the first cleavage took place inside the membrane, the cleavage plane being always at right andes to the common diameter of the two protoplasmic drops (Fig. 16). (Only when the nuclear-spindle had already formed, at the time of the F"^" 16- bursting of the membrane, were there exceptions to this rule.) A peculiarity of the first cleavage was that the protoplasm was always divided into a larger sphere (I, Fig. 16), and a smaller sphere (II) which was connected with the Please note that these images are extracted from scanned page images that may ha
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