It has been recognized that the invertebrates, especially Octopus are difficult to keep for a long time in an aquarium with closed circulating system.
In order to find out the cause of this difficulty, the present studies are carried out by investigating the influence of nitrate accumulated in culturing water with low pH values and with low alkalinity values on Octopus, since accumulation of nitrate, reduction of alkalinity and increase of hydrogen ion concentration are known to be some of remarkable characteristics in the long aged sea water of an aquarium with closed circulating system.
When nitrate in accumulated in culturing water, accompanied with low alkalinity and with high hydrogen ion concentration of the water, siphoning movement of Octopus cultured in that water becomes more frequent than in natural sea water (Table 1), and the decrease of the oxygen uptake rate due to reduction of oxygen content of the water starts at higher oxygen levels (Fig. 5).
The facts mentioned above confirm that these changes in quality of the long aged sea water form some of causes of the difficulty in question.

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Electrical stimulation of the excised eye of 11 marine teleosts leads us to conclude that the lens movement in accommodation is directed temporad in 9 species or dorso-temporad in 2 bottom feeders, though the movement sometimes tends to have the component toward the bottom. This component was concluded, however, to be an artifact brought about by strong contraction of the muscles in the iris, ciliary body, etc. due to a strong stimulation. The temporal movement of the lens means that the visual axis is directed forward, and dorso-temporad means lower-forward. These directions of the visual axis are consistent with the habits of the fishes. Musculus retractor lentis of carp and goldfish is very feeble, and no movement of the lens was elicited by the electrical stimulation.

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1. The presence or absence of any seasonal correlation between the distribution of polysaccharides in the otolith fluid of fish and the zone formation of otolith was examined by means of paper electrophoresis. The specimens of both rainbow trout and flatfish were used.
2. In the otolith fluid of each species, an hyaluronate-like substance and PAS-positive materials, possibly neutral heteropolysaccharides, were commonly found in the state of complex forms with proteins. Sulfated mucopolysaccharides were also detected throughout the year in rainbow trout and at the period of opaque zone formation of the otolith in flatfish, respectively.
3. There was no seasonal change which suggested the presence of any clear correlation between the electrophoretic distribution of these polysaccharides in the otolith fluid of the fish used and the zone formation of the otolith. However, both acid mucopolysaccharides and PAS-positive materials, together with proteins, are con-sidered to be components essential to the formation of organic matrix of otolith itself.

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The fishing gear used in the Bering Sea in 1963 by the subsidiary trawlers belonging to the factory ship, namely, the Danish seine trawl net (the eastern net) and the two-boat type trawl net (the western net) were studied comparatively on the following items: the height of net-mouth, the sweeping area of towing-rope, the filtering capacity of towing-net, in relation to the fishing efficiencies of the net.
The results obtained are as follows:
1) By the radar measurements, it was ascertained that the sweeping area of towing-rope belonging to the western net was wider than that of the eastern net; the ratio being about 1.4.
2) According to the results obtained by the model experiments executed at the circulation tank, the height of net-mouth of the western net was larger than that of the eastern net; the difference was about 0.6-2.Om in the full scaled net. The filtering capacity of towing-net of the western net was larger than that of the eastern net; the ratio being about 8.9.
3) Judging from the catch per one set of towing-net, it was assumed that the catch of the western net was bigger than that of the eastern net, which was coincided with the contents of the above mentioned datas, but counting on the catch record in a unit sweeping area of towing-rope and in a unit filtering capacity of towing-net, it was ascertained that concerning the fishing efficiency the eastern net is superior to the western net.

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1. The flesh of Lepidocybium flavobrunneum and Ruvettus Pretiosus has been analyzed, and were both found to contain approximately 20% of oil consisting primarily of wax.
2. The flesh and acetone-soluble oil of both species produce seborrhea besides diarrhea in rats, and are judged not suitable for food.
3. The acetone-soluble oil has been fractionated into the hydrocarbon, wax, glyceride and polar substance fractions by column and thin-layer chromatography, and alcohol and fatty acid constituents of wax and glyceride fractions analyzed by gas-liquid chromatography.
4. The main constituents present are: cetyl alcohol, oleyl alcohol and oleic acid in wax and oleic and eicosenoic acids in glyceride.
5. Hydroxy oleic acid is not recognized, differing from the observation of Cox and REID on the oil of R. pretiosus.

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In order to establish the chemical nature of volatile acidic odors produced by Clostridium botulinum during growth, volatile fatty acids were determined by gas chormatography in the cultures of cooked meat broth inoculated with each strain of the six toxin-types. The results were as follows:
1. Acetic, propionic, n-butyric, iso-butyric, n-valeric, iso-valeric (iso-valeric and/or active α-methyl-butyric), and iso-caproic acids were identified in the cultures of type A, B and F. The branched acids except iso-caproic acid were deduced to be the metabolic products derived from some branched amino-acids by “Stickland reaction”.
2. Acetic, propionic, and n-butyric acids were identified in both the cultures of types Cβ and D. A high proportion of propionic acid among the resulting fatty acids suggests that these organisms appear to obtain some of their energy by propionic acid fermentation similar to that displayed by propionibacteria.
3. n-Butyric acid, in higher proportion, as well as acetic acid were identified in the cultures of type E, suggesting that this organism obtains most of its energy by butyric acid fermentation similar to that displayed by butyric acid bacteria.
Further the chemical nature of the off-odor of foodstuffs contaminated with botulinal toxin was examined. An abnormally high proportion of n-butyric acid, being responsible for the “butyric” off-odor, was found in home-made “Izushi” of raw fish and rice cake, which had caused an episode of human type E botulism. Also a high proportion of propionic acid, as well as acetic and n-butyric acids were found in raw whale meat, which had caused an outbreak of type Cβ botulism in mink.
Accordingly, the patterns of the volatile fatty acids presented by each type of Clostridium botulinum seem to be reflected in that of foodstuffs contaminated with respective type of the organisms.

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