Morphological studies on secretion in the silk glands of the caddis fly larvae, Platyphylax designatus Walker.

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Actively secreting silk gland cells of caddis fly larvae show the following fine structure: a well developed rough-surfaced endoplasmic reticulum, continuity between roughsurfaced and smooth-surfaced endoplasmic reticulum adjacent to the Golgi saccules, dense material (secretion) in the margins of the Golgi saccules, some of which appear in the form of blebs and discrete membane bounded secretion granules; the latter seem to coalesce and migrate to the surface of the cell where they are discharged. Intracisternal granules appear in glands where the secretion cycle has apparently been interrupted. These observations suggest a secretion cycle for the silk glands comparable to that demonstrated by both morphological and experimental methods in certain other protein secreting cells: namely, synthesis by the ribosomes, transport to the Golgi complex through the cisternae of the endoplasmic reticulum, concentration by the Golgi complex and movement of the secretion granules through the cytoplasm to the surface of the cell where they are discharged.