The fine structure of cockroach blood cells.

Electron-mictoscopic observations of the blood cells (Haemocytes) in the legs of the cockroach Blaberus discoidalis reveal three 'types' of cells distinguishable on the basis of fine structure. One type of cell contains numerous membrane-limited opaque bodies which may be lysosomes. A second type contains abundant digestive vacuoles and appears phagocytic. A third type, frequently encountered in rewlymoulted untanned animals but less often observed in mature adults, contains membrane-limited tubule-containing bodies (TCB) filled with rows of 340 A tubules which are quite different from cytoplasmic microtubules. It is suggested that haemocytes containing TCB may be equivalent to the coagulocytes (cystocytes) of light microscopy which actively participate-in-the process of haemolymph coagulation in Orthoptera. No attempt whatsoever is made at classification. Since considerable overlap in fine structure exists between cell types, it seems probable that the electron-images of fixed cells observed in this study represent several morphological expressions of which an individual cell may be capable during its lifetime.