摘要：

FIG. 2. Photomicrographs of embryos. (a-h) Nomarski optics, Microflash, anterior to left. Bar = 10 pm. A few landmark features are marked on the photographs, but no attempt has been made to label all the cells; for reliable identifications the line drawings should be used, preferably in conjunction with at least some tracing of the lineage. (a) Just before first cleavage. Midplane. Male and female pronuclei are apposed; first polar body visible beneath eggshell at anterior end (where it typically but not invariably resides). (b) Beginning of gastrulation. Left lateral aspect, midplane; cf. Fig 5. Ea and Ep are moving dorsally, into the interior. P1 is recognisable by its small size, by the germinal plasm or nuage (arrowed; Strome and Wood, 1982; Krieg et al, 1978) around its nucleus, and by the distinctness of its nuclear membrane. (c) Late gastrulation (ca. 210 min). Ventral aspect, superficial plane; cf. Fig. 6. The cleft through which the MS cells have just entered is starred. (d) ca. 280 min. Dorsal aspect, superficial plane; cf. Fig. 7a. Small neuroblasts anteriorly; larger hypodermal cells, loaded with granules, posteriorly. Furrows can be seen between hypodermal cells (cf. Fig. 10). White arrow, dying ABarpaaapp; black arrows, ADEshL and ADEshR. (e) ca. 260 min. Ventral aspect, superficial plane; cf. Fig. 7b. Small neuroblasts over entire surface. Dying cells (arrowheads) are engulfed by their sisters (arrowed): ABplpappaa, ABplpppapa, ABprpppapa. (f) ca. 280 min. Dorsal aspect, midplane. int, cylinder of intestinal cells, nine nuclei in this focal plane, cytoplasm heavily loaded with granules; ph, cylinder of pharyngeal cells, less distinctive, contain few granules. (g) First movement (ca. 430 min). Left lateral aspect, midplane; cf. Fig. 8c. int, intestine; ph, pharynx; white arrowhead, anterior sensory depression; black arrowhead, rectum; arrows, dorsal hypodermal ridge, heavily loaded with granules. (h) Threefold, rolling. Only the anterior two-thirds of the embryo is in focus. White arrowhead points to mouth, linked by pharynx (ph) to intestine (int). Arrows

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