Hemolymph cells of Orconectes virilis were stained during the months of August to November by a variety of histological and histochemical techniques. Cells were classified as hyaline cells, small granulocytes, and large granulocytes. Presence of mitochondria1 enzymes was indicated by tests for succinic dehydrogenase and cytochrome oxidase. Reaction to test for the hydrolytic enzyme, leucine acyl naphthylamidase was intense in the granules of the large granulocytes. The PAS reaction indicated a mucopolysaccharide at the cell membrane. Lipid was found in all three hemolymph cell types of Orconectes virilis at the time of this study.
Although several previous morphological studies of the hemolymph cells of crustaceans have been made, the role of these cells in the total economy of this invertebrate group has not been clearly defined. Among the first recorded observations of crustacean blood cells were those of Carus (1824), who called them ameboid wandering cells. The characterization of these formed elements into two types, granular and nongranular (hyaline) amoebocytes, followed with the studies of Haeckel(l857). Confirmation of the presence of two basic cell types in the hemolymph of various species of crustaceans is extensive in the literature (Halliburton, 1885; Cuenot, 1891;Hardy, 1892; Kollman, '08; George, '41; George and Nichols, '48). Although the terminology used is confusing, most authors agree that nongranular or hyaline cells, 9-15 w in diameter; and a series of granulocytes, ranging from 9-35 0 in diameter, are the basic cell types in the hemolymph of crustaceans. Toney ('58), using phase microscopy, recorded the presence of these two basic cell types, as well as transitional cells. Toney designated four cell types; lymphoid cells, monocytes, and two explosive granulocyte forms. Earlier, Cuenot (1891) had suggested that the granulocytic cells were merely mature hyaline elements. Bruntz ('05, '07) also claimed that the hyaline cells represent the first stage of development, followed by