Some observations on concentrically structured, intracellular granules in the hepatopancreas of the shore crab Carcinus maenas (L.)

The R, F and B cells of the hepatopancreas of Carcinus maenas are derived from undifferentiated (E) cells at the distal end of the tubules. Observations with the scanning electron microscope on freeze fractured tubules show that (a) most of the concentrically structured granules are confined to the R cells with few in F or B cells, (b) within individual R cells, granules are of similar size, and (c) the further R cells are situated from the distal end of the tubule, the greater is the mean diameter of the granules that they contain.