. The beginnings of embryonic development : A symposium organized by the Section on Zoological Sciences of the American Association for the Advancement of Science, cosponsored by the American Society of Zoologists and the Association of Southeastern Biologists, and presented at the Atlanta meeting, December 27, 1955. Embryology. S. RANZI 297 intestinalis) may develop into exogastrulae (Ranzi and Ferreri, 1945) (Fig. 7). In some of these larvae the notochordal cells do not differentiate. In some other larvae notochordal cells may ap- pear with little difference from entodermal cells. It is conc
. The beginnings of embryonic development : A symposium organized by the Section on Zoological Sciences of the American Association for the Advancement of Science, cosponsored by the American Society of Zoologists and the Association of Southeastern Biologists, and presented at the Atlanta meeting, December 27, 1955. Embryology. S. RANZI 297 intestinalis) may develop into exogastrulae (Ranzi and Ferreri, 1945) (Fig. 7). In some of these larvae the notochordal cells do not differentiate. In some other larvae notochordal cells may ap- pear with little difference from entodermal cells. It is concluded, therefore, that there is an entodermization of notochordal cells induced by LiCl. NaSCN-treated embryos show a larger neural plate. In Ascidia malaca embryos, treated with LiCl, Nieuwkoop. Fig. 7. Exogastrula from Li +-treated embryo of Ciona: ec, ectoderm; en, entoderm; mi, myoblasts. (1953) found only exogastrulae of the second type.* I did not have the opportunity to study the material further, because I deemed it suflBcient to find certain malformations in ascidians corresponding to those of vertebrates. * Nieuwkoop (1953) interprets the organization of exogastrulae without notochord by admitting that intrinsic differentiation tendencies, extrinsic realization factors, and tissue affinities are required for embryonic differ- entiation, and that realization factors are blocked by LiCl. Perhaps Nieuw- koop's realization factors represent the demoUtion of preexisting protein structures inhibited by L1C1, as discussed Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original American Association for the Advancement of Science. Section on Zoological Sciences; Tyler, Albert, 1906-. Washington
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