Fine structure of the clitellum of the annelid Enchytraeus fragmentosus

The clitellum of the annelid worm Enchytraeus fragmentosus was found to consist of two distinctive granular cell types in addition to the cells typically found within the epidermis. One cell type possessed granules containing microtubules. The other cell type had large secretory granules which fused and filled most of the cell. The contents of these granules were established to be responsible for the secretion of the cocoon wall and the nutritive substance surrounding the egg.