Title: American malacological bulletin
Identifier: americanmal6719881990amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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156 AMER. MALAC. BULL. 6(1) (1988) proximal part of the "arm"; both cells show invaginations in- to the other cells. The "head" (the tip of the micraesthete cell) is slightly swollen and also contains mitochondria. The distal part forms numerous microvilli towards the subsidiary cap (Fig. 13). The "head" can show a high degree of vacuoliza- tion in some micraesthetes, but this zone does not continue into the "arm". SUBSIDIARY CAP. In contrast to the apical cap, the sub- sidiary caps appear continuous at their outer and inner sur- faces. They also consist of organic material. They contain in- ner pores (width = 0.1 /*m), but in nearly all cases they are closed to the outside, as well as to the interior of the micraesthete, by continuous sheets. The distal sheet is up to 0.2 /tm, the proximal sheet about 0.1 fim wide. In some cases the micraesthete cap has been dam- aged by organisms. In these cases, parallel sheets of vary- ing thickness are placed underneath the remainder of the cap. Sometimes, the subsidiary cap is completely replaced by this structure. PERIPHERAL CELLS. The peripheral cells surround the
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Fig. 7. Longitudinal section of an aesthete nearly completely filled with the granules of secretory cells (si, secondary lysosome). Fig. 8. Base of a secretory cell (nu, highly condensed nucleus; sg, secretion granule). Fig. 9. Distal tip of a secretory cell after secretion. Surrounding cytoplasm (arrows) and small cytoplasmic remains are visible between the former secretion granules. The interior is now continuous with the extracellular material underneath the apical cap, in which microvilli and cilia (double arrow) of central cells are embedded (c, central cell).

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