. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. GASTRULAT1ON IN SAND DOLLAR 293. Figure 8. Scanning electron micrographs of the cells in the arch- enteron after the completion of invagination: Hemicentrotux pulcherrimus (A-C); Scaphechinus mirabilis (D-F). Top (A. D). middle (B. E). and bottom (C, F) levels of the archenteron are shown. The cells in the archenteron of H. pulcherrimus are cuboid, while those in S. mirabilis are elongated along the apico-basal direction. Note that the wall of the arch- enteron is thicker in S. mirahilis than in H. pulcherrimus. The scale ba
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. GASTRULAT1ON IN SAND DOLLAR 293. Figure 8. Scanning electron micrographs of the cells in the arch- enteron after the completion of invagination: Hemicentrotux pulcherrimus (A-C); Scaphechinus mirabilis (D-F). Top (A. D). middle (B. E). and bottom (C, F) levels of the archenteron are shown. The cells in the archenteron of H. pulcherrimus are cuboid, while those in S. mirabilis are elongated along the apico-basal direction. Note that the wall of the arch- enteron is thicker in S. mirahilis than in H. pulcherrimus. The scale bar indicates 10 jim. this is the case, immobilization of the ectodermal layer should affect the invagination process. To test this possibil- ity, the change in the length of the archenteron was moni- tored in gastrulating embryos attached to a glass dish coated with poly-L-lysine. H. pulcherrimus gastrulae attached to the poly-L-lysine coated glass dish (Fig. 11 A). If the embryos had been under- going primary invagination when attached, the invagination was slowed and tip of the archenteron could not reach the apical plate. However, the embryos gastrulated almost nor- mally if they had been attached after primary invagination. In these cases, the rate of archenteron elongation was not different from that in control embryos (Fig. 1 IB). In contrast, the invagination process was greatly affected in 5. mirtibilis embryos. If the embryos were not pressed usuinst the bottom of the 2lass dish usina a class needle. they did not firmly attach to the glass dish. Embryo II shown in Figure 12 loosely attached to the glass dish, so that its position changed during observation. In this embryo, invag- ination occurred almost normally. On the other hand, em- bryos I, III. and IV were rather firmly attached to the glass dish. In these embryos, invagination of the gut rudiment was considerably delayed. Nonetheless, embryos III and IV re- started invagination when they detached from the glass di
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
