Though many taxonomic studies on the japanese Lepidotrigla had been made by several authors, most of them were not sufficient in the treatment of variation of the specific characteristics. Therefore, the resultant uncertainties in the identification embarrassed the population studies of the fishes belonging to the genus.
Accordingly, in order to make clear the specific characters, I engaged in an observation of a fresh body and in the measurement of several parts of body in the present paper, which was based on the large numberrt of specimens collected from the commercial landings of the Eastern Sea trawlers from 1948 to 1950.
In the pattern of the innerside of pectorals, six types are distinctly recognizable as shown in Plate I, though they are somewhat divergent. In order to make clear the specification of each types, from the viewpoint of morphometry, I chose the measured value of the individuals falling in the interval of 15±1cm in their standard length. (Thus, I unified the size approxi. mately, and avoided the error caused by a difference in their size.) As the frequency distribution of these values could be regarded as nearly normal type (see Fig. 1), I computed the rejection limit for each item under 5 per cent level of signlificance, to indicate the thresholds of their variation. If these limit separated from each other perfectly, I regarded them as distinct species morphometrically. According to the above mentioned standpoint, the types A, B, C, E and first group of F are separated clearly, as illustrated in Fig. 2. (Here, type F was divided into two different groups by the measured value, for instance, that of rostrum as I showed in this figure.) But the types B, C and second group of F overlapped each other in variation, and I cannot assert the distinctness of these groups in the natures dealt with in Fig. 2. While, in Fig. 3, the separation is perfect between the second group of F and the types B, C. Therefore, it may be concluded that the groups of type A, B, C, E, F (I): and F (II) respectively are distinct ones, not only from their pectorals pattern, but also from the morpho. metrical data. Type D is excluded from the present treatment, because it is quite a rare species, and is not important economically.
Next, I examined the relation between the above mentioned groups and the species hitherto described. And obtained the following result: namely, type A group correspond to L. japonica, type B group to L. guentheri, C to L. kishinouyei, D to L. punctopectoralis, E to L. microptera, F (I) to L. alata, and F (II) to L. abyssalis.
When we identify the samples, though the method is somewhat troublesome, it is possible to do it by the measured values of several parts of body using Fig. 2 and 3, which were made for every section of the size of the fish, as a chart for the key of species. On the other hand, the patterns of the innerside of pectorals are available as a guide for species, and these patterns can be recognize in the individuals of smaller size, even in 50mm length. According to the latter method, it is rather difficult to divide the two groups of type F. However, one group of type F, L. alata, can be easily and unrnistakablly distingushed from the other group of L. abyssalis, by its large triangular rostral process. The latter method of identification can be made by inspection irrespective of the size of fish.

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When a mantle piece of Mytilus edulis is bathed in M/2 KC1 solution for 5 minutes, a conspicuous, discharge of sexual product is induced in about 1 hour after the treatment. If KC1 solution here used is alkalified by NaOH, the spawning is much accelerated, while if acidulated by HC1, it is inhibited. When a mantle piece is treated with acidic sea water before the KC1 treatment, it is delayed to begin in its spawning, whereas a mantle piece is bathed into acidic sea water after the treatment of KC1, the number of eggs decrease suddenly in its discharge. It may be logical conclusion that K ion is easy to penetrate into cells of ovary in alkaline medium, while it is difficult in acidic medium. The penetration of much K ions into cells may cause the excitation of the ovary. The eggs must be discharged abundantly by the excitation of ovary. Thus KC1 treatment of mantle piece in acidic medium is much powerful to inhibit its spawning.

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Mantle pieces of Mvtilus edulis were bathed for 10 minutes in M/2 aqueous solutions of KC1, NH₄C1, NaC1, LiC1 and in M/3 solutions of BaCl₂, SrCl₂, CaCl₂ and MgCl₂ respectively. Of all these chemicals, KCl, NH₄Cl and B₃Cl₂ induced the spawning, while the others did not. K, NH₄ and Ba ions have higher mobility, therefore they must have higher permeability through the cell membrane than the other ions. In exchange with such cathions penetrated into the cells of ovary, H ion, possessing the highest mobility among the cathions, may go out of the cell. When the cells interior may become alkaline, the spawning may be induced.

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Mytilus edulis contains the gonsd in almost all parts of the mantle except the muscular margin. The spawning could be induced even in this mantle piece by sudden rise of temperature from ca. 7°C to ca. 15°C. Numerous mature eggs were discharged from the cut ends of genital canal after about 1 hour of temperature rise. This spawning may be considered due to the increased permeability of the ovarian epithelium. The enhanced permeab ility may be supposed to alkalify temporally the interior of cells and thus the discharge will be induced just like the case to bathe the mantle in ammoniacal sea water.

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