On cross-section of dorsal fin-rays of Caprodon schlegeli (GUNTHER), Sardinia melanosticta (T. & S.), and Scomber japonicus HOUTTUYN, resting- zones are found. The cross-sections are made by ordinary histological method embeding in paraffin after decalcification by 10% nitric acid diluted by 10% formalin, stained with Delafield's Hamatoxylin, Mayer's Satires Hamalaun, and Hamatoxylin-Eosin, and cut out in 8-10 microns by means of a mlcrotome. The resting zones of S. melanosticta appear stained deeply by Hämatoxylin (Fig. 2, B), and those of S. japonicus found stained light violet (Fig. 2, C). The growth zones of S. japonicus appear dyed light red. But those of C. schlegeli are very indistinct (Fig. 2, A). The number of the resting zones and the growth-ratio between the resting zones occuring on the cross-sections of the fin-rays appear to be largely corresponding to those found on the scales in, at least, S. melanosticta and S. japonicus (Tables 1-4). But this trait seems to be less valuable for the purpose of fishery-biology of such fishes given above by the reasons given below, viz, it is difficult by the present method to make the cross-section for study of a large number of individuals of the fish for which observations may be done, and in addition to this no standard point available for measurments useful for back-calculation of body-length is present.
The principal characteristics of the scales of Carassius carassius (Fig. 1) (including Gold fish and “Tetsugyo”) are that their radial grooves (=radii) meet together in the focus, distinct lateral grooves are observed, their basal margin has strong waves, their grooves do not increase so much in number when they have grown up, and the regenerated scales (Fig. 2 & 3) have remarkable anastomosing network grooves in the focal area. The princical characteristics of the scales of Cyprinus carpio (Fig. 4 & 5) are that their grooves approach to the focus, but never meet together, basilateral grooves are often generated, but lateral grooves in their true sense are hardly to be observed, and as the fish grows innumerable supplementary grooves are generated, which outnumber those of Carassius carassius. The ordinary scale of the hybrid of these two fishes are (Fig. 6), on the whole, of an intermediate type in scale character: some of the grooves approach towards the focus, but do not meet together, lateral grooves usually are not observed on them, their regenerated scales (Fig. 7) are more similar to those of Carassius carassius, having focal network grooves, though the network is rather imperfect. This scale character is parallel to the fact that the other structures of the hybrid show intermediate features between these two fishes, as reported by Dr. Y. MATSUI. Of what significance it is that the hybrid was born between Cyprins carpio and Carassius carassius which belong to their respective different genera and species and that its stn.ctures display in the mostpart an intermediate from between the two I cannot understand. But unless a law that a hybrid can be made between near related but different genera or species is acknowledged, I cannot agree with the view that genus Carassius and genus Cyprinus should be comprised in the same genus, i. e. Cyprinus carassius, . merely because a hybrid can be made between them. Giving more credit for the fact that the structures of regenerated scales of the two fishes are distinctly different than the facts that a hybrid can be made and that its characteristics are of the intermediate nature, and noticing that there is phylogenetically a considerable distance between these two fishes, I am convinced from the lepidological point of view that they should be classified into their respective different genera and species.
Volcano Bay is situated on the south-western coast in Hokkaido and in known as one of the most important fishing grounds. This paper is a report on fishes obtained by the writer in the environs of the bay during these two years. The fishes treated here belong to 50 families, including 116 genera and 141 species. Influenced by the warm current (Kuro shio) from the south, 85 species are temperate forms, while on account of the cold current (Oya shio) from the Kurile Islands, 56 species are boreal ones, the latter being mainly found northwards from northern part of Japan proper and Hokkaido. As to the distribution, the fact agree with the observation on medusae made by. UCHIDA (1940). In the following list the temperate forms are marked with an asterisk.