. The Biological bulletin. Biology; Zoology; Marine biology. 328 SVEN HORSTADIUS R. Isolation of aui In two cases Zeleny (1904) successfully separated the four animal cells of the 16-cell stage (ani) from the twelve lower (an2 + vegi + vegz). The two ani-larvae possessed an apical plate but were not reared long enough to show the differentiation in detail. Twenty-five ani were isolated. One did not develop very well. Fourteen disappeared altogether (cf. p. 319), and the remaining 10 developed into blastulae with apical organs (Fig. 7). Five of them had one flagellum, 3 had two flagella, and 2
. The Biological bulletin. Biology; Zoology; Marine biology. 328 SVEN HORSTADIUS R. Isolation of aui In two cases Zeleny (1904) successfully separated the four animal cells of the 16-cell stage (ani) from the twelve lower (an2 + vegi + vegz). The two ani-larvae possessed an apical plate but were not reared long enough to show the differentiation in detail. Twenty-five ani were isolated. One did not develop very well. Fourteen disappeared altogether (cf. p. 319), and the remaining 10 developed into blastulae with apical organs (Fig. 7). Five of them had one flagellum, 3 had two flagella, and 2 none. I had the impression that the pit in some cases was missing or not so pronounced as in normal pilidia, but this observation may be erroneous. It may be mentioned that Yatsu (1904), in the uncleaved egg, localized the basis. Fig. 7. A-D. Larvae from the isolated four most animal cells of the 16-cell stage: ani. E. Isolated veg2 (the four most vegetative cells of the 16-cell stage). of the apical organ, not in the animal pole, but in a broad zone a little above the equator. Wilson (1903) also observed flagella without ectodermal pit, namely in larvae from vegetative egg fragments. There is need of further elucidation of the question whether the absence of the ectodermal pit in ani-larvae, if this takes place, has any relation to the localization suggested by Yatsu. If so, it would indicate a trace of dependent differentiation. The ectoderm of these ani-blastulse was ciliated in the usual way. At the pole opposite the apical organ they had small fields of ciliated band tissue (high, yellowish cells). In some cases this field had the form of a protrusion, with the ciliated band like a girdle round it (Fig. 1, D). I interpret this to mean that the patch of ciliated band tissue in ani corresponds to that part of the normal band which, on the basis of our staining and transplantation experiments, we ascribed to the ani-cells (See Fig. 3).. Please note that these images are extra
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