Several kinds of double sheet net were tested for salmon drift-net fishing. They were specially designed for experimental operation and are constructed by the body of net with small mesh and outer wall with large mesh. The body and the wall of the net are about the same in depth and are connected each other with short hanging lines at appropriate positions.
Three different kinds of such double sheet net were prepared by adjusting mesh size of of wall net and length of hanging lines that connect body and wall together. These were put on experiment on board the Kitagami-Maru in the North Pacific Ocean during the 1961 fishing season. Two different types of double sheet net and single sheet net without wall were also tested in 1962 on board the Shinyo-Maru.
On the basis of the results obtained from these experiments, 142±14% increase of salmon catch is expected by appending an outer wall that has mesh size three times larger than that of body net.

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1. Amino acid composition of mucous substances in the extrapallial fluid forming the nacre of Pinctada martensii and Hyriopsis schlegeli were compared with that of conchiolin of the nacre, respectively.
2. Some of protein fractions or amino acid residues of the mucous substances may decrease or lose during denaturing to form the organic matrix of the nacre and so mineralizing.
3. Alanine and glycine residues in the nacreous conchiolin were five times as much as those in the fluid. This result may suggest that the protein fractions in the fluid corresponding to nacrosclerotine and nacroine are incorporated in conchiolin at a very high rate.

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Five kinds of sulfonamides, sulfamerazine, sulfisomidine, sulfisoxazole, sulfadimethoxine and Sulfamonomethoxine were given orally to the rainbow trout, and the concentrations in the tissues were then studied.
The experiments were made on the rainbow trout yearling of its average body weight being from 75 to 80gr.. The individual fish was given one of the above sulfonamides 250mg. per one killogram of the body weight in a single dose, and therafter the concentrations of sulfonamides in plasma, liver, muscle and kidney of the fish were determined by the Bratton and Marshall modification method. The water temperature in the rearing tanks varied between 7.2 and 15.0°C.
The results were all summarized in Tables 1 to 5, and Figs. 1 to 3, showing that the absorption of sulfonamides into the fish tissues, when compared with the one in mammals, was taken place neither quickly nor fully, while the sulfonamides maintained their effective level in the tissues for a long time. Out of the sulfonamides tested sulfomonomethoxine and and Sulfamerazine were well absorbed, and they continued to be effective a good while. Sulfisomidine and Sulfisoxazole, on the other hand, were soon excreted after a temporary abiding in the tissues. Nearly no absorption was observed in the case of Sulfadimethoxine. As for the concentration level of the sulfonamides in the tissues, except for sulfamerazine, the highest value was seen in liver, corresponding about double the one in plasma and kidney, while the muscle level was as low as half the plasma level.

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In the previous paper¹⁾ it was reported that the rainbow trout did not uptake so much of sulfonamides in a free form into the tissues as the mammals do. Therefore, the experiments in the present report were conducted on the absorption of sulfonamides of water soluble salt by the rainbow trout tissues.
The rainbow trout yearling with the average body weight of 78gr. were orally given the free form sulforamides of 250mg per one killogram of body weight in a single dose, and the concentration levels were then measured in plasma, liver, muscle and kidney of the fish by the use of the Bratton and Marshall modificated method. The experimental fiish were kept in the tanks of the water temperature from 9.8 to 15.0°C.
As is seen in Tables 1 to 2 and Figs. 1 to 2, the sulfonamides in sodium salts gave the higher concertration level in sulfamonomethoxine and sulfamonomethoxine than the free form sulfonamides did. It is to be noted that even sulfadimethoxine which was hardly absorbed by the fish tissues in the application of a free form of it, raised its concentration in plasma by ca. two times.
No difierence in the distribution way in the tissues and also in the acetylated rate was observed between the fish given sulfonamides in the free forms and in the sodium salts.

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In order to examine gross-anatomical changes of the brain components of yellow-tail with their body-growth, an observation was made on the specimens of four stages, larval, young, immature and adult. Total number of the specimens used are 102, the total length of them ranging from 10mm to 1, 100mm.
The main results obtained are summarized as follows.
1) Most remarkable changes of the following two stages.
(a) Notable growth of each of the corpus cerebella, valvula cerebelli and eminentia granularis was observed in the fish of a transitional stage of their behaviour shifted from a rather planktonic life at the sea surface to a life travelling under floating seaweeds; total length of the fish at this stage was measured to be 30-50mm.
(b) Conspicuous growth of the corpus cerebelli, valvula cerebelli, eminentia granularis and crista cerebelli was found in the fish of the other transitional their behaviour shifted from a life travelling under floating seaweeds to free-swimming life; total length of these fish was 100-150mm.
2) These results suggest that in yellow-tail there exists an intimate correlation between the behavioural modification and the morphological changes of some brain components, especially of the corpus cerebelli and valvula cerebelli.

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Characteristics of a vibrio isolated from diseased young of Ayu, Plecoglossus altivelis, in salt-water were determined as well as ability of the bacterium to produce experimental infections. The organism was methyl-red negative, V-P positive, failed to grow on MacConkey's agar and was pathogenic for freshwater Ayu and eels, producing typical symptoms of red disease in the latter, but not for mice. With the characteristics and pathogenicity determined, the bacterium was classified as Vibrio anguillarum.

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For surface gillnet fishing it is important to know about the horizontal movement of salmon, particularly to know the direction and distance of the movement during one night.
Two net strings were set at right angles to each other to determine the direction of the movement of salmon off the west coast of the Kamchatka peninsula, i. e. sets were made in north-south and east-west directions as shown in Fig. 3.
The shape and the direction of the net strings were delineated from photographs of the echo image of the corner reflectors which were mounted on the gillnet (Fig. 2 and Fig. 3). The numbers of fish gilled and the side of the net from which they entered were estimated in each shackle of the net as it was hauled in.
The experiments were performed on the training ship “Hokusei Maru” of the Faculty of Fisheries, Hokkaido University, in early July 1965.
The results obtained are summerized as follows;
1) The gillnet string was changed to various directions and distances during the period from set to haul (Fig. 3).
2) The catching ratio on the south side of the nets for both pink salmon and chum salmon was most dominant (Table 4 and 5). By considering the relation between the catching ratio and the direction of net lay, it can be presumed that the direction of movement of salmon in this area is a predominantly northward movement.
3) Because of the remarkable difference in the catching ratio due to the direction of the net lay, it is considered that the salmon move a straight way during one night.

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Absorption spectra of cooked tuna meat were determined directly, after addition of sodium hydrosulfite, and after further addition of nicotinamide by using a spectrophotometer equipped with an opal glass apparatus^{1, 2)} . On reduction with sodium hydrosulfite, the cooked meat was observed to become intensely pink giving the absorption spectrum fairly characteristic of ferrohemochrome. After further addition of a small amount of nicotinamide, the meat bore the spectrum typical of ferrohemochrome, indicating an additional formation of ferrohemochrome (Fig. 1).
In the case of heat-denatured myoglobin, the typical spectrum of ferrohemochrome appeared only when treated together with reducing agent and nicotinamide (Fig. 2). Therefore it is likely that myoglobin, when heated, is not converted to a denatured globin hemochrome, but to a pigment having room for co-ordination with nicotinamide. The pigment seems to correspond to “metmyochromogen” presented by TARLADGIS³⁾, of which the fifth and sixth co-ordination positions are occupied by denatured globin and water molecule. Such a conception should facilitate to solve above-mentioned phenomenon.
On the basis of these observations, the pink color of cooked meat is considerd attributable for a mixture of “metmyochromogen” and hemochrome, co-ordinating denatured globin and a nitrogenous base inherently present in the meat. Standing on this view point, the improvement of the pink color of cooked meat by addition of nitrogenous bases and reducing agents can be reasonably explained assuming the additional formation of ferrohemochrome from the “metmyochromogen”.

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The amino acid composition of the hydrolysate of photosynthetic bacteria, Rhodo-pseudomonas capsulatus, was analyzed automatically by using the amino acid analyzer and it was found that in the bacteria, histidine, proline, alanine, valine, methionine, tyrosine and tryptophan were present in larger amounts than in Chlorella vulgaris and yeast, Saccharomyces anomalus. Especially, the content of methionine was much higher; 5 times more than chlorella and 3 times more than yeast.
This work was supported by the grants from the Ministry of Education.

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1. A toxic substance possessing a strong mydriatic activity was found in the mid-gut gland of the Japanese ivory shell, Babylonia japonica, collected at Numazu, Yokohama and Kamakura. A sample from Teradomari on the Japan Sea side where an outbreak of poisoning occurred in 1957 was found to be non-toxic.
2. An assay method for the ivory shell toxin based on mydriasis of mice was established.
3. The toxin is soluble in water, slightly soluble in methanol and ethanol and insoluble in most fat-solvents. It is unstable to heat, especially in an alkaline medium, dialyzable through a cellophane membrane and not steam-distilled. The purified toxin is positive for the ninhydrin reagent, fluorescent under ultraviolet light and negative for the Dragendorff and biuret reagents.

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In the present paper deals with the estimation of the free amino acid composition of Ulva pertusa, Enteromorpha linza (green algae), Undaria pinnatifida, Sargassum confusum (brown algae), and Chondria crassicaulis, Neodilsea yendoana, Laurencia nipponica (red algae) using an amino acid analyzer (Hitachi, type KLA-III, Amberlite CG 120). The results obtained are shown in Table 2.
Amino acid composition of Ulva is in good agreement with that of Enteromorpha in rich amount of D-cysteinolic acid and less amount of taurine, tyrosine, tryptophan, arginine, and lysine. None of alloisoleucine, citrulline, histidine, methionine, ornithine, and S-hydroxy-methyl-L-homocysteine are found in these two species.
High contents of alanine, glycine and proline in Undaria, those of alanine in Sargassum, chondrine in Chondria, taurine in Neodilsea, and glutamic acid and valine in Laurencia are specifically recognized. A few amount of alloisoleucine is found in Undaria, whereas chondrine observed in every species of these algae. Citrulline is present only in Neodilsea, ornithine in Sargassum, Neodilsea, and Laurencia. S-Hydroxymethyl-L-homocysteine is found in Neodilsea and Laurencia in appreciable amounts, but D-cysteinolic acid is not detected in these algae. The presence of some unknown compounds is suggested from the present study.

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1. p-Aminobenzoic acid and inositol were eliminated individually from the basal diet used by HALVER et al., and the requirements of young carp for the vitamins were studied.
2. In feeding trials for 16 weeks, no deficiency symptom of p-aminobenzoic acid was observed. Moreover, addition of sulfanilamide to the diet revealed no effect on growth and numbers of erythrocytes. From these results p-aminobenzoic acid is concluded to be nonessential for young carp under the experimental conditions.
3. The deficiency symptoms of inositol were characterized by skin lesions, loss of appetite and retarded growth. The younger carp indicated the deficiency symptoms at a higher rate than the elder ones. There were some distinct indications of supply of the vitamin by biosynthesis.
4. Under the experimental conditions adopted, the requirement for inositol was found to be 7 ?? 10mg per kg of body weight per day (44mg per 100g of diet) on the basis of body weight gain.

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1. Niacin was eliminated from the basal diet devised by HALVER et al., and the requirement of young carp for the vitamin was studied.
2. In two feeding trials lasting respectively for 8 and 10 weeks, the deficiency symptoms were characterized by poor growth, loss of appetite, hemorrhage in the skin, and high mortality.
3. When the niacin-deficient group was divided, the section receiving the complete diet indicated the recovery of growth and disappearance of the deficiency syndromes.
4. Under the experimental conditions adopted, the requirement for niacin was found to be 2.8mg per 100g of diet or 0.55mg per kg of body weight per day according to the body weight gain.

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