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Among the diverse repertoire of reproductive behaviors shown by sculpins, copulating behavior is known to occur in some species (Breder and Rosen, 1966). Most of these copulating sculpins transfer sperm by using a huge flexible penis (Morris, 1952; Ragland and Fischer, 1987; Munehara, 1988). However, the little dragon sculpin Blepsias cirrhosus, whose penis is too diminutive to be noticed, and the Japanese sea raven Hemitripterus villosus, which does not possess such a functional genital organ, also have been inferred to copulate on the basis of histological observations of eggs collected from, their ovarian cavities (Munehara et al., 1991). It is not clear, however, by what means the sperm of these fishes are actually transferred from the male into the female's ovarian tract. The present study, therefore, was undertaken to clarify this issue by observing copulating and spawning behavior of H. villosus in an aquarium.

A LTHOUGH the sea raven, Hemitripterus americanus Gmelin, has been known to science for more than 150 years, comparatively little has been recorded about its early life history. Bean (1897, et. seq.) made observations on the eggs of this species in the New York Aquarium on November 29, 1897, Tracy (1910) mentioned a large specimen with ripe ova taken off Rhode Island December 22, 1908, and Huntsman (1922) recorded young collected in the Bay of Fundy in the summer. Bigelow and Welsh (1925) reported ripe females taken in November and December from southern New England, as well as 13/4-inch (45 mm.) fry which were collected from the bottom in the same region during the summer. Bigelow and -Schroeder (1936) provided additional evidence that H. americanus is a late fall and early winter spawner by reporting that specimens taken on Nantucket Shoals in June had gonads only partially developed. They also discussed early growth and the number of eggs per female, citing observations both from southern New England and the coast of Maine.