In 1941 a parasitic fungus was first observed on the eggs of many obtained from natural spawning areas in Chesapeake Bay (Sandoz, Ro Newcombe, 1944). Dr. John N. Couch of the University of North Car examined infected samples and recognized the parasite to be a new sp he named Lagenidiiin callinectes Couch (1942). Marked annual fluctuations in the commercial catches of the blue crab C sapidus Rathbun (1895) have taken place. The discovery of the e raised the questions of how it affects the development of the crab em percentage of the eggs of a crab may be infected, and how widely th distributed in Chesapeake Bay. Conceivably, such a parasite could serious biological factor limiting the production of crab larvae and cau in part, yearly fluctuations in the commercial population. Laboratory and field studies were carried out: (1) to ascertain the of existence of the parasite in the individual crab eggs as well as on an mass (commonly called "sponge"); (2) to show how readily infection m mitted under certain conditions; (3) to indicate the effects of salinity ture on the survival and development of the fungus; and (4) to show Chesapeake Bay in which it occurs and the approximate degree of infe Acknowledgment is made to all persons who aided in this study. Sp are expressed to Professor John N. Couch of the University of North Car identified and described the fungus parasite; to Mr.

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