The U. S. Fish and Wildlife Service is perturbed because of the reduction in numbers of the soft-shelled clam, Mya arenaria, along the coast of New England (Glude, 1955). The writer is studying the parasites of the clam and of its predators (Stunkard, 1951, 1953, 1957, Stunkard and Uzmann, 1958) in an attempt to discover the causes of the decline and possible biological measures for control of the principal predators, the green and horseshoe crabs, Carcinides maenas and Limulus polyphemus. Mya arenaria harbors the asexual generations of digenetic trematodes, including the sporocysts and cercariae of Cercaria myae Uzmann, 1952. These larvae were shown by Stunkard and Uzmann (1958) to be developmental stages of a species of Gymnophallus, whose sexual generation occurs in shore-birds. The asexual stages invade the digestive and sexual organs of the mollusk, limiting or terminating its reproductive activity. The clams also serve as intermediate hosts of other trematodes and 3 species of metacercariae occur commonly in the gills and palps. The life-cycles and bionomics of these worms are now under investigation. Since the asexual generations of these metacercariae must occur in mollusks which live in the immediate vicinity of the infected clam, an attempt is being made to find and identify them. Furthermore, since the definitive hosts of these metacercariae are animals that feed on M. arenaria, examination of shore-birds has been started. To obtain information on the sexually mature stages, metacercariae have been fed to laboratory-raised birds: chicks, eider ducks, herring gulls and common terns, as well as to mice and hamsters. The clams and other mollusks, the eider ducklings, and a sampling of shore-birds were provided by Walter R. Welch, Chief of Clam Investigations, Boothbay Harbor, Maine, under whose authority the study is conducted. Grateful appreciation is here expressed to him and members of his staff.