The Ultrastructure of Circulating Hemolymph Cells of the Marine Snail Cerithidea californica (Gastropoda: Prosobranchiata)

Two morphologically distinct blood cell‐types, the granulocyte and hyalinocyte, are found in the hemolymph circulation of the marine prosobranch Cerithidea californica . Granulocytes, measuring 12.7 µ (9.0–15.0 µ) in diameter, possess well‐defined ectoplasmic and endoplasmic regions of the cytoplasm, granules of moderate to heavy electron density, tubular rough endoplasmic reticulum (RER), short vesicles of smooth endoplasmic reticulum (SER), and a large cytoplasm to nucleus ratio. Two morphological variants of this cell‐type are distinguished depending upon the presence or absence of dense granules or RER. Hyalinocytes, measuring 5.3 µ (4.0–8.0 µ) in diameter, are distinguished from gran ulocytes by possessing a smaller cytoplasm to nucleus ratio and a general lack of dense cytoplasmic granules and SER.