File:The Biological bulletin (20369488562).jpg

Title: The Biological bulletin
Identifier: biologicalbullet178mari (find matches)
Year: [1] (s)
Authors: Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983
Subjects: Biology; Zoology; Biology; Marine Biology
Publisher: Woods Hole, Mass. : Marine Biological Laboratory
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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14 V. J. MARTIN
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Figure 6. Cross section of a 10-h planula. The embryo consists ot'an ectoderm (EC), an acellular meso- glea (M), and an endoderm (E). The endoderm is composed of an outer columnar epithelial layer (G) surrounding a central core of lightly staining interstitial cells (arrows). The ectoderm contains epithelio- muscular cells (dark-staining cells) and glandular cells (light-staining cells), but is devoid of interstitial cells, nematoblasts, nematocytes, and ganglionic cells. X320. Figure 7. Endodermal region of a 10-h planula. Clusters of interstitial cells (arrows) occupy the central endoderm. EC, ectoderm; G, epithelial layer of endoderm: M, mesoglea. • 320. anterior-posterior axis. These lightly staining, oval- shaped interstitial cells possess a large, centrally located nucleus with one to several nucleoli. Dark-staining gran- ules occupy the cytoplasm of these young interstitial cells, however, such granules disappear as the cells ma- ture. Interstitial cells of late planulae possess few granules (see Fig. 2). Interstitial cells traverse the nematocyte differentia- tion pathway in the endoderm (see Figs. 1, 2, 8). Such cells are distinguished by the appearance of either a dark- or light-staining nematocyst capsule. The capsule en- larges to an extent that it displaces the nucleus to one side of the cell. A few endodermal nematoblasts, confined to the anterior and middle two-thirds of the endoderm. have been observed in the 10-h planula. Interstitial cells traversing the neural differentiation pathway have not been seen in the immature planula. Interstitial cells and nematoblasts emigrate as single cells from the endoderm to the ectoderm. Interstitial cells migrate out from all locations along the planular endo- dermal axis, whereas outward nematoblast migration is confined to the anterior and middle endodermal regions. Interstitial cells and nematoblasts first appear in the planular ectoderm at 14 h postfertilization (Martin and Archer, 1986). Their ectodermal distribution corre- sponds to their above-mentioned migration patterns. Immature planulae (10 h) do not express a FMRF- amide-like antigen as indicated by their lack of staining. Yininxphimtla (24 h postfertilization) By 24 h, the planular ectoderm contains epithelial cells (epitheliomuscular, glandular, and sensory), interstitial cells, nematoblasts, a few nematocytes, and ganglionic cells; the endoderm has gastrodermal epithelial cells, in- terstitial cells, and nematoblasts. Both interstitial cells

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