The Formation of the Ootheca by Periplaneta americana II. The Structure and Function of the Left Colleterial Gland

The anatomy of the left colleterial gland of the cockroach is described. It is convenient to subdivide the gland into four regions. At the posterior end, abutting on to the outlet of the gland, there is no secretory activity and the cells of this region are not unlike normal epidermal cells. Anterior to this region are the three secretory regions of the gland; of these, the anterior and posterior secrete the structural protein and the constituent cells are equipped with a complex end-apparatus, a thick-walled depression in the apex of the cell in which the final stages of the elaboration of the secretion occur. The body of the end-apparatus contains canalicules which lead to the lumen of the gland. Alkaline phosphatase is abundantly present in this organ. Protein is secreted continuously, and there is no cycle related to oviposition. The third region, between the protein-secreting regions, secretes an oxidase, whose function may well be to oxidize the phenolic tannin-precursor produced in the right colleterial gland when the products of the two glands come together at oviposition. The gland becomes fully functional some 14 days after the final moult, the immature cells of the nymph developing directly into mature cells characteristic of the region in which they occur. Within each of the main regions the cells show some differences which suggest that there is a wave of change passing along the gland. It appears that the cells of the anterior end of the gland become defunct and the hitherto inactive cells of the posterior end take on a secretory function. The structural protein has a high phenolic content, and contains no combined carbohydrate. The presence of lipoid in the secretory cells appears to be directly bound up with the secretory processes.