. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 92 A. OKUSU. Trunk Cauda! region Figure 14. Larvae after hatching from the egg capsule (3 days after ovipositon. 1-day-old larvae), (a) Ventral view of the larva with three distinct body regions: ciliated pre-oral apical cap, unciliated trunk, and ciliated caudal region, (b) Vegetal (caudal) view of the trochophore larva showing the small imagination of the stomodeum on the ventral side of the trunk. AT, apical tuft; CD, cerebral depression; Pt, prototroch; Sd. stomo- deum; Tt. telotroch. appears to be secretory, because the
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 92 A. OKUSU. Trunk Cauda! region Figure 14. Larvae after hatching from the egg capsule (3 days after ovipositon. 1-day-old larvae), (a) Ventral view of the larva with three distinct body regions: ciliated pre-oral apical cap, unciliated trunk, and ciliated caudal region, (b) Vegetal (caudal) view of the trochophore larva showing the small imagination of the stomodeum on the ventral side of the trunk. AT, apical tuft; CD, cerebral depression; Pt, prototroch; Sd. stomo- deum; Tt. telotroch. appears to be secretory, because the cilia-free membranes covering the globules were often ruptured (Fig. 2la, b). The globules appeared iridescent under the light microscope. The globules disappeared at metamorphosis, as the apical cap and the caudal region were withdrawn into the trunk (Fig. 24b). One to two hundred small epidermal papillae appeared on the trunk (Figs. 19a, 23a. 24b). Like the globules mentioned above, these papillae are suspected to be secretory in func- tion. Unlike the globules, the papillae persisted after meta- morphosis (Figs. 24b. 25a). Protonephridia were not ob- served in the light micrographs of semithin sections. Nen'ous system. The cells underneath a pair of depres- sions on the pretrochal region of the apical cap on the future ventral side of the adult (Figs. 14a. 17, 19a, 22a, 23a, b, 24a. 27, 28) became internalized to differentiate into definitive cerebral ganglia (Fig. 22b). These depressions were free of white globules, but the surface ciliation was not different from that of the rest of the apical area (Figs. 17, 22a). Pedal ganglia arose (Fig. 22b); however, the process by which they were formed is uncertain. Development of terminal sense organs was not apparent, although may have been present. Metamorphosis Larvae aged 7 to 8 days: beginning of metamorphosis. In spite of active ciliary movement of the prototroch and apical tuft, larvae at this point were no longer able to s
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
