Proctoeces maculatus (Looss, 1901) ODHNER, 1911 (Trematoda: Fellodistomidae), is described from Wakkanai, northern Hokkaido, Japan. Adults were obtained from the rectum of the fishes, Myoxocephalus stelleri, Limanda schrenki and Platichthys stellatus. Sexually immature worms were found in the midgut of the fish, Sebastes schlegeli. Nonprogenetic metacercariae were found in the kidney of the snails, Neptunea arthritica and N. intersculpta constricta. The life cycle of this species in northern Hokkaido waters is briefly discussed. P. subtenuis (LINTON, 1907) HANSON, 1950, P. major YAMAGUTI, 1934, P. lintoni SIDDIQI et CABLE, 1960, P. buccini LOOS-FRANK, 1969, P. scrobiculariae LOOS-FRANK, 1969, P. hawaiiensis YAMAGUTI, 1970, and P. ichiharai SHIMURA et EGUSA, 1979, are regarded as synonymous with P. maculatus. P. ostreae FUJITA, 1925, and P. magnorus MANTER, 1940, are considered species inquirendae. A list is given of 15 other trematodes species obtained from fishes at Wakkanai during this study.

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A new species of cyclopoid copepod, Cyclopina kiraensis, is described and illustrated on the specimens collected from intertidal area near the mouth of the Yahagi-furukawa River in Mikawa Bay, the Pacific coast, Central Japan. The species is most closely related to C. esilis BRIAN, 1928, but differs from it in the structure of antenna, mandible, swimming legs 4 and 5, and other diagnostic particulars.

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Chironomus javanus is a widely spread species in Southeast Asia and Micronesia. The northward advancing of this species, especially the penetration to the Japanese Islands recently comes into notice. Since 1981, a sporadical occurrence of this species is found in Honshu, Japan. This paper deals with morphological and biological notes based on the Japanese materials of C. javanus. Immature forms and the egg mass of this species are described for the first time.

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The taxonomic relationship of the two morphologically very similar seaurchins, Temnopleurus toreumaticus and T. hardwickii was examined by means of the gel electrophoresis of enzymes. The results demonstrated that the two species shared no common allozymes at 5 of the 15 genetic loci and that the genetic identity value (7=0.667) observed between the two species was comparable to those already reported between sibling species or very closely related species of many other animals. These electrophoretic data are not consistent with the views of earlier echinoid taxonomists that these two forms are conspecific or that each belongs to the different genus, and strongly support the generally accepted view that they are distinct but very closely related species.

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Placentela crystallina REDIKORZEV, 1913 has been noted as one of the remarkable representatives of tunicates showing the formation of placental structures, but its morphology is given rather incompletely and its systematic position has been unsettled. On the other hand, Sigillinaria clavata OKA, 1933 is proved to bear the placental membrane as in P. crystallina. Close examinations of the type specimen of P. crystallina, the specimens of S. clavata identified by OKA and other related specimens made S. clavata sink to a junior synonym of P. crystallina. Structures of the placental membrane, probably functioning as a resting bed for embryos, are presented here in detail. P. crystallina is also unique among the ascidians provided with the postabdomen (containing at least epicardium and gonad), in having the heart situated along the posterior part of intestinal loop. The taxonomic significance of this structure seems to lead to the conclusion that P. crystallina is better placed provisionally in the subfamily Euherdmaniinae of the family Polyclinidae.

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