This report is to describe the experimental results of the five stern trawlers about A-maru (314 ton 1200 hp), B-maru (1500 ton 2700 hp), C-maru (2800 ton 3150 hp), D-maru (2900 ton 3150 hp) and E-maru (3000 ton 3500 hp). They were built in our country recently. The relation between the shaft horse power (B. H. P.) and power to pull trawl (E. H. P.) is approxi-mately
E.H.P.=K(B.H.P.)
number of K of A-maru is 0.18, B-maru C-maru D-maru are 0.22 and E-maru is 0.27.
The table 1 and 2 show the sizes fo the experimental trawlers and trawl fishing gear. The measuring equipment is shown in the Figs. 1-3 and the experimental results of the pulling power of the stern trawler are seen in the table 3 and Fig. 4.

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From an experiment on the layer of the scale (Fig. 1), the following results were obtained:
(1) Both the hyperbolic and the elliptic laminae have two foci near the margin of the anterior part, as shown in Fig. 1-A and B.
(2) The thickness of the enamel layer does not change within a range of R (Fig. 2) from 3 to 8mm (Fig. 5).
(3) On the variations of the number of ridges per fibrous lamina are shown in Table 2. The number approaches 4 in larger scales.

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The present paper deals with the seasonal histological changes in the gonads of the purple snail, Purpura clavigera, known as an enemy of young oysters and clams.
The materials used were collected every 21st day from the beach of Niigata on the coast of the Japan Sea. The period of collection extended from April to December, 1963.
Vitellogenesis begins in this mollusc in April or early in May, and the ovum reaches a ripe state in early in July. As the ovary matures, periphery of the nucleus of ovum is sur-rounded chiefly with smaller yolk granules, while the eccentric zone of the ovum is occupied by larger ones. Up to the breeding season, smaller granules around the nucleus change into larger ones. There is no detectable change of the amount of yolk granules during and after the breeding season, however a considerable number of young oocytes which may have origi-nated from the residual oogonia are recognized in the cystic wall (ovigerous fold).
During April to early May, the testis is filled with spermatogonia and spermatocytes, and the formation of spermatids takes place in the latter part of May. The highest activity of the spermiogenesis is reached early in July. Cells in various stages of spermatogesis are found throughout the year, however, Accordingly, the breeding season of the present species extends from late spring to summer, although it is difficult to decide histologically a precise period of spawning.
There appeared two types of regression in the gonads after the breeding season. Many of the specimens inspected carefully show that the glands become degenerated by degrees. On the contrary, in a small number of the specimens regarded as the senile ones hole glands degenerate very rapidly.
It is very interest to find out many strange spherical cells in the seminiferous tubules. The cells contain granules stained deeply with hematoxylin (and anilin blue). According to histochemical examination the granules in question probably are of mucopolysaccharide (Feulgen negative but PAS positive etc.). A marked increase in the amount of the granules is encountered as the ovary matures. During breeding season these cells are pushed forwarded into the vas defference together with the sperm. It is not yet determined whether or not the cells are ejected into the vagina of the female. It seems likely that the cells are homologous to the so-called free-cell reported by Nishiwaki¹⁵⁾ of a very related species, Purpura bronni.

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Eels taken from eel-culturing ponds in August and November were starved for three months at temperatures of 28 and 12°C, respectively.
Oxygen consumption rate did not changed in relation to the duration of starvation. Nitrogen excretion, however, lowered remarkably during the initial 15 days, followed by a constant level, in three month starvation either at the high or low temperature.
Relative liver weight of starved eels decreased rapidly during the initial 15 days followed by a nearly constant level at the high temperature, while at the low temperature it decreased at a rather constant rate throughout the experimental period of three months. The same tendency was also observed with the liver glycogen and the liver fat.
It was found that weight, glycogen and fat of eel liver undergo more rapid and pronounced changes than those of carcass particularly in the early stages of starvation.
Among three reserved substances, glycogen, fat and protein, glycogen shows the most rapid decrease in the course of starvation.

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Numerous aspects of the wet acidic digestion procedure for the assay of chromic acid in a small amount of feed and excreta were examined to study the digestibility of feed by marine fishes; these examined were the spectral absorption curves of solutions prepared by the wet acid digestion of chromic oxide (Fig. 1), the stability of chromic acid solution obtained (Tables 1, 2), the effects of the amount of perchloric acid added (Table 2) and the wavelength to pre-pare the concentration-optical density curve (Fig. 2).
The results of the present work showed that the following procedures were adequate for the study of digestibility. Weigh 50-100mg sample containing 1-3mg chromic oxide, wrap in a piece of filter paper and transfer to a dry 100ml Kjeldahl flask. Add 5ml of concentrated nitric acid in such a manner that it will wash down the particles adhered on the inside of the flask and allow to stand for a short period. Heat flask over a micro-electric heater which has the holes in the asbestos board covered so as to allow more heat to come in contact with the flasks. Allow the sample to digest until white precipitate is obtained (for about 20 minutes). When black particles adhere to the neck or side of the flask, wash them down by turning the flask 180°. Turn off the heater, cool the flask and 3ml perchloric acid to the digestion mixture and then reheat until green colour changes to yellow, orange or red. The reversal change in colour frequently occurs if the flasks are cooled just after the change in colour from green to yellow, because of the insufficient oxidation of the content. Therefore, the extension of digestion for 10 minutes is necessary after the colour change. Cool slightly and add about 50ml distilled water. Cool to room temperature and make up to 100ml in a volumetric flask with distilled water. Allow to stand for a few minutes to precipitate inor-ganic material. Transfer solution gently from the volumetric flask to a colorimetric tube, and read optical density at 350mμ
against distilled water. The standard curve obtained by the wet acid digestion technique is expressed by the following equation;, Y=0.2089X+0.0032, where Y is the optical density at 350mμ
, and X is the chromic oxide content of the sample (mg/100ml).

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A series of experiments on the purse seine was carried out by model net. In this paper, the author analyzed the influence of pursing velocity during the pursing operation.
The model net and the apparatus used in this experiments are shown in Figs. 1 and 2.
The results obtained are summarized as follows:
(1) When the pursing operation is done fast in the case of A (Fig. 1), the corks of the bunt section are pulled into the water at the final stage of the pursing operation. However, in the cases of B and C (Fig. 1), the corks do not sink and the netting is kept in a normal form.
(2) The tension of purseline during the pursing operation is summarized in Fig. 6 and the relations between the pursing velocity (v) and the tension (T) of purseline are shown as T=av (Fig. 7).

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This report dealt with the daily reports during the entire season in 1963 by 22 of the Danish seiners belonging to one of the fish-meal fleets which fished in the Bering Sea. The stratification of the records of daily catch per boat according to the area, the depth, and to the grade of daily haul made it possible to find the following tendencies:
1. The frequency distribution of daily catch per boat yielded by the same grade of daily hauls in the same depth zones was in most of the strata agreeable to the normal series, but that yielded by the highest grade of daily haul in few of the depth zones was kept in the logarithmic normal series (cf. Figs. 1 and 2).
2. The bathymetric difference of daily hauls made it difficult to get a good result of that of daily catch yielded by the same grade of daily haul.
3. In the same depth zone of the same area, the daily catch per boat was poorer on the days when the boats conducted frequent hauling than on the days when the boats conducted less frequent hauling (cf. Fig. 2).
4. These findings and the deviation of the daily hauls in the same depth zone suggested such possibility that the frequency distribution of daily catch per boat in the same depth zones of Area A or B composed of many strata of the records with different average of daily catch, and the distribution before stratification according to the grades of daily hauls approximated superficially to the logarithmic normal series.

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Vibrio parahaemolyticus, a causative organism of food poisoning in Japan, is known to be widely distributed in the coastal sea areas, and it is supposed that fish and shellfish may be previously contaminated with the organism in sea water before landing. In the present study the authors investigated the multiplication of the organism on the flesh samples of various kinds of fish and shellfish according to the following procedures.
The sample of about 10g flesh placed in a 300ml conical beaker was inoculated with a small amount of the cells, approximately 10³, and was kept in an incubator at 33°C. After being incubated for a certain period, the cells developed on the sample were suspended in a certain amount of diluent, 3% NaCl water supplemented with 0.1% peptone, by means of a homogenizer or a shaking method, and the determination of the number of the organism was made using “a modified TCBS medium”, which was diviced for the selective colony counting of biotypes 1, 2 and 3 of Vibrio parahaemolyticus according to SAHEKI et al.¹⁾.
Results were summarized as follows:
There was no multiplication of the organism in the case of red muscled fish such as tuna, skipjack or mackerel etc., in which pH of the flesh was generally below 6.0, whereas remarkable multiplications of the organism were observed in so-called white muscled fish, fresh water fish, shellfish, squid or octopus, pH of the flesh was above 6.0. The population de-veloped in 7 hours incubation amounted to 10⁷to 10⁸. Therefore, the occurrence of the bacterial growth depends upon the pH value of the flesh.

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The changes of the carotenoids concentrations in the skins and fins were followed on a guarnard, Chelidonichthys kumu, (Hobo in Japanese), and rockfish, Helicolenus hilgendorfi, during ice storage and on another guarnard, Lepidotrigla giintheri, (Kanado in Japaneses) during freeze storage at temperatures of -3°C, -18°C, and -30°C.
1. A practically good retention of the carotenoids concentrations was observed in Hobo guarnard for four to five days and in rockfish for seven to eight days by ice storage. After these periods, they began to attenuate their coloration and the rate of decay accelerated particularly after incipient spoilage was conceived in the fishes.
2. Stability of the pigments in these fishes differed with species. Hobo guarnard revealed a more rapid rate in the discoloration. In both fishes, the discoloration occurred much faster in the skins than in the fins.
3. A red pigment, astaxanthin, was found less stable in the tissues of Hobo guarnard than yellow pigments.
4. Freeze storage with a keeping temperature of -3°C indicated a considerable disoloration in Kanado guarnard after 35 days. And, a temperature of -18°C or even -30°C was not able to arrest the discoloration after rather longer period such as 50 and 75 days.

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In a previous paper¹⁾, it was reported that carps are able to synthesize Lascorbic acid from D-glucose and D-glucuronolactone. In the present study, the conversion of myo-inositol to L-ascorbic acid by carps has been investigated by means of radioactive tracer techniques. The results obtained are as follows:
1) After injection of myo-inositol-U-¹⁴C into carps, the specific activities of the visceral ascorbic acid were determined. From the data in Table 1, it is evident that carps are able to convert myo-inositol to L-ascorbic acid.
2) The visceral ascorbic acid labeled with ¹⁴C was identified to be L-form by paper chromatography (Fig. 1).
3) The ascorbic acid recovered from the carps administrated with uniformly labeled myo-inositol-¹⁴C was degraded to determine the activities of the constituent carbon atoms. The results (Table 3) show that uniformly labeled myo-inositol-¹⁴C was converted to uniformly labeled L-ascorbic acid-¹⁴C.

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It has been reported by the authors¹⁾ that the sialic acid-like substances (positive substance to “direct EHRLICH reaction”) were obtained from both the external mucous substance of an eel, Anguilla japonica, and the cartilage of a hammerhead, Sphyrna zygaena. The present work was undertaken to make clear the chemical properties of these two substances. From the absorption spectra of those substances by some colour reactions specific for sialic acid, the ultraviolet absorption spectra of those and the acid- or alkali-treated derivatives of N-acetylneuraminic acid, and from the paper chromatograms of the degradation products of the sialic acid-like substances, it was suggested that the two substances are the degradation products of the sialic acid by the mild acid hydrolysis during the extraction from the materials. It seems most likely that the sialic acid-like substance of an eel is a heavily degraded product and that of a hammerhead a slightly degraded one.

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