1. Rotting resistance of cotton, sun hemp, Italian hemp, sisal, manila and coir twines immersed in Cochin backwater has been determined.
2. The values of rotting coefficient K in TAUTI'S formula log T/T₀-T=-(K log e)+ Const. were calculated from the results obtained by the experiments and it was confirmed that the value of K is inversely proportional to the diameter of twines dipped. The values of K worked out are as follows:
and
Higher the value of K, the rotting would be quicker.
3. Number of days N till a twine loses half of its original breaking strength is proportional to the diameter of the twine dipped in water, i. e. N=αD. Where a is constant and when D the diameter is in mm, N=6.50 D for cotton
=5.75 Dfor sun hemp
=2.55 D for Italian hemp
=6.00 D for sisal
and =7.40 D for coir.

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In the present study the characteristics of the fishing grounds on the bottom gill-net fishery were discussed using the results of our test nets and those of commercial fishing from 1956 to 1959 as a part of the works which had been undertaken to clear the present states of coastal fisheries and the biological characteristics of their resources. For the porpose of this research the sea around Tomioka, Kumamoto Prefecture was divided into three fishing grounds-inner bay (Tomoe Bay), outer bay (Tomioka Bay) and open sea (Amakusa-nada) (Fig. 1).
The results obtained from this study are as follows:
1) The outer bay is more similar to the open sea than the inner bay, and the inner bay different remarkably from the other grounds in character (Figs. 3, 4, 6 and 7).
2) The inner bay is characterized by Inegocia japonica, Gerres japonicas and Ditrema temmincki, and in the open sea Panulirns japonicus, Stephanolepis cirrhifer and Chrysophrys major are dominant, and the outer bay is represented by Stephanolepis cirrhifer, Girella punctata and Ditrema temmincki (Fig. 5).
3) The open sea is the largest of the three fishing grounds in the productivity and stability in the catches, and the inner bay is the smallest (Figs. 6, 7 and Table 1).

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Since the previous report in 1953¹⁾, the use of the resting pool in eel-pond has become popular, and almost all the ell-ponds in Kawashiri district (Fig. 1) are now equipped with it. The 86 eel-ponds at the district out of 204 were observed as to the size, area, water supply and utilization of vertical pump and agitator. For the 12 resting pools of different types selected, studies were made on diurnal change of water temperature, disolved oxygen, NH₄-N etc. Results are summerized as follows:
1. The resting pools are generally 40-70cm in depth and take increasingly a form of rectangle and are supplied with well water mixed from creek (Table 1).
2. The resting pools measure 50-60m² in surface area or about 1.3% to 4, 500m² of the rearing ponds.
3. The resting pools may be divided into 3 types by their water circulation: the running water type (Fig. 2), semi-circular type (Fig. 3) and circular type (Fig. 4).
4. During summer time, the water of creek or well supplied 40-70l/sec. in the pools at night, kept the temperature of pool water 4-6°C lower and the disolved oxygen 0.9-3.8 cc/l higher than those of the rearing pond.
5. There are no apparent trouble or difficulty in keeping 3.2-12tons of eel in a resting pool of 50-60m² at night which is supplied with above mentioned amounts of water and it saves safely the eel from their “gulping”.

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In the PETERSEN-type tagging experiment, the type C systematic errors caused by the abnormal behavior of the tagged fish, give the bias to the estimate of fish population size.
The author introduces the tagged ratio methods to remove such a bias, under the following assumptions,
1) type C systematic errors affect the vulnerability of the tagged fish during some intervals after the liberation.
2) the ratios of vulnerability of the tagged fish to that of untagged fish in these intervals are constant (Eqns. 5 ?? 8, 10 ?? 11, 12 ?? 13 and 14 ?? 15).
Some examples for calculation by these methods are also shown (Tables 1 ?? 4 and Figs. 1 ?? 10). And the results are compared with that of by the previous methods (Table 5).

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The author, having reported in his previous papers^10)-15) extraction, refining, molecular distillation and concentration by saponification of vitamin oil and esterification of vitamin A alcohol studied in the aspect of fundamental conditions influencing their results as well as in that of important points taken care of in practicing them on industrial scales, now gives a description of the experiments he carried out to determine the stability of vitamin A contained in vitamin oils subjected to these various kinds of treatment, the stability being evaluated in accordance with the length of time in which a sample of vitamin oil is reduced by half in respect of its vitamin A content.
In the first place, the stability of vitamin A was compared among liver oil samples obtained from different sources but equally by alkali digestion. As seen from the results of experiment presented in Table 1, liver oil preparations obtained from sharks come out top and those from cods and pollacks, tunas, giant bass and whales follow them in this order in respect of the stability of vitamin A content. It seems likely that the stability order here found is the reflexion of the readiness of undergoing the alkali digestion or in other words the difficulty in removing the natural antioxidative accompaniment of these sources of vitamin A.
In the second place, the influence of refining method on vitamin A stability of refined vitamin oil was examined with liver oil specimens obtained by subjecting a crude sample of pollack liver oil to various refining schemes illustrated in Fig. 1, the results being presented in Table 2. As obvious from the table, as for the stability of vitamin A content to be assigned to different methods of refining vitamin oil here examined, crude liver oil comes out top and a liver oil sample subjected merely to filtration, that refined by means of alkali, that treated with acid, that processed with alcohol and that treated with diatom earth come in this order in succession to crude liver oil, the order being again suggestive of the difference in strength of removing natural antioxidant among these types of refining method.
In the third place, the effect of molecular distillation as a means of concentrating the vitamin A in liver oil on the stability of this vitamin in distillate oil was inquired by examining the stability of vitamin A with samples of raw oil before distillation, those of distillate fractions respectively obtained at different temperatures and those of residual oil remaining after distillation, the results being shown in Tables 3 and 4. It is seen from these results that, irrespective of whether the source of liver oil is shark or whale, a vitamin oil fraction distilled at the lower temperature has the greater stability of vitamin A, while raw oil shows a value in respect of the stability of vitamin A content, which falls between the stability values for Fractions 1 and 2 both distilling at rather low temperatures. Although the stability of residual oil could not accurately estimated from some reasons, the above-mentioned results for distillate fractions and raw oil seem to be sufficient to suggest that natural antioxidant in liver oil can distill rather earlier than vitamin A.
In the fourth place, the products respectively obtained in different working stages of the process wherein a vitamin oil previously concentrated by molecular distillation is subjected to concentration by saponification and the vitamin A alcohol thereby produced is further esterified were examined of their stability of vitamin A content, the results shown in Table 5 being obtained. As seen from the table, concentrated products of vitamin A alcohol prepared from different sources equally show values of stability as good as those found for a pollack liver oil obtained by the alkali digestion method.

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As regards the fact that the quality and quantity of fat present in food is a potent influence on the cholesterol value of serum, there is adopted in general, as a conclusion drawn from a number of investigations with human beings as well as with test animals, a view that said action reflected in the lowering of cholesterol value of serum is characteristic of such fats as containing unsaturated fatty acids in a great proportion.
The author, aiming hereupon at a fuller utilization of the oil obtainable from viscera of aquatic animals, tried to prepare a product comprising mixed ethylesters of polyunsaturated fatty acids. The procedure be followed in the present work comprises subjecting the residual oil remaining after taking out vitamin A from liver oil by molecular distillation to ethanolysis to cause the production of mixed ethylesters of fatty acids (see Fig. 1), distilling the mixed esters into several fractions (see Table 3) and correctively treating the distillate fractions coming out in a temperature range from 180°C to 220°C to cause the separation of new fractions to be realized in accordance with their tendencies of forming addition products of urea (see Fig. 2). The author succeeded by this procedure in concentrating the polyunsaturated fatty acids contained in pollack liver oil into mixed ethylesters thereof, obtaining from an oil sample having an iodine value of 169.8 a preparation of mixed ethylesters with an yield of 16.5%, based on the amount of sample, the iodine value of which was estimated as 310.8 and the fatty acid constituent of which was gaschromatographically found to consist up to 77.19% of fatty acids of C₂₀ and above (see Table 4).
Next, to examine the reductive effect on cholesteral value of serum, the above obtained preparation of mixed ethylesters of polyunsaturated fally acids was internally applied to a group of rats as test animal while two other groups of rats were feed with a hydrogenated coconut oil and safflower oil as control substance and referential one, respectively, both of which were used similarly to said preparation of mixed esters as added to feed (see Tables 1 and 2). When the groups of rats were measured every one weak throughout the first 4 weeks of their body-weight (see Fig. 3), their contents of plasma cholesterol (see Fig. 4), plasma phospholipid (see Table 5) and total liver cholesterol (see Fig. 6), the following situations were illumined as results of the measurements:
1) As for the increase in body-weight, the rat group dosed with mixed ethylesters of polyunsaturated fatty acid was lower in the rate of increase as compared with other groups of rats.
2) About the values of plasma cholesterol and C/P ratio, i.e., the ratio of the amount of plasma cholesterol to that of plasma phospholipid, the rat groups dosed with safflower oil and the residual oil in molecular distillation, respectively, showed fairly smaller values and the rat group dozed with mixed ethylesters of polyunsaturated fatty acids gave by far smaller values as compared with control rat group.

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Beta-apo carotenal was fed to rat and rainbow trout. The results obtained were as follows.
1. Two different doses, 0.3 and 30mg, of apocarotenal were fed daily to each of vitamin A deficient rats for 19 days. The latter dose accelerated the growth. A cryptoxanthin-like pigment and a colored fatty acid were detected in the livers of the latter group of rats, though apocarotenal was found nowhere in the body of the animal.
2. In case of rainbow trout 0.3 and 30mg of apocarotenal per kilogram of the body weight were fed daily for forty days. No change in body color was observed, though the flesh was tinted with slight brownish orange.
The brownish orange pigment, as it was insoluble in organic solvents, seemed to be different from carotenoid. Between two groups of the trout fed with or without apocarotenal, no perceptible difference was seen in the contents of carotenoid and vitamin A in their skin, flesh and liver.

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Vitamin A was determined on many rainbow trout samples collected on various occasions. Cultured fish showed a greater fluctuation in vitamin A content than the wild fish. Vitamin A in the former ranged from 0.23 to 770 IU per gram of liver and 8 to 800 IU per 100 grams of muscle, while in the latter, from 13 to 430 IU per gram of liver and 23 to 160 IU per 100 grams of muscle. Though some of the cultured fish were rich in vitamin A, the others were found with an extremely low level of the vitamin, namely 144 to 250 IUper kilogram of the body weight, or only one-tenth as low as that of puffers, jack mackerel, etc., which have been known as the poorest fish in vitamin A.
Vitamin A in the diet seems to have a great effect on the vitamin A level of rainbow trout, but probably little on the growth of the fish. In many samples, the vitamin A content of the muscle oil changed in proportion to that of the liver oil. The similar tendency was also found in other various kinds of fish in the authors' previous data. Occurrence of some points aberrant from majority of the samples as shown in Fig. 1 may be explicable by a postulation that the liver always precedes muscle in varying its vitamin A level. In other words, a time lag phenomenon in varying the vitamin A level between the liver and muscle may be the cause of scattering of dots in Fig. 1. However, it is likely that vitamin A in the kidney oil changes more proportionally with that in the liver oil than the vitamin in the muscle. Some additional data on the vitamin A in brook trout and landlocked salmon is given in Table 4.

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In the previous report, it was described that separation of the alcohol extract of the green meat or dark meat of albacore or yellowfin tuna by paper chromatography gave a spot of a substance of peptide nature producing yellow color with ninhydrin.
When raw green meat was boiled with a reducing compound added, the spot was no longer detectable on the chromatogram. When the substance separated from the extract of green meat was mixed with raw meat paste of good quality and the mixture boiled, such phenomena as discoloration and giving characteristic odor were observed, whereas the remaining extract was proven to be free of such action.
Thus, the substance producing yellow color with ninhydrin appears to be directly associated with development of green meat of tuna when subjected to boiling.

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All of the existing theories of drying of a solid body have neglected the effect of the decrease of thickness due to the loss of water from the solid during drying. This decrease, however, seems to become noticeable for the case of fresh fish muscle.
This paper presents the theory of drying accompanied with shrinkage, with special interest to the drying of fresh fish muscle. The fundamental equation of this problem subject to appropriate initial and boundary conditions becomes non-linear and thus the method of moment is applied in solving the equation. The results obtained show that the drying curve accompanied with shrinkage is steeper than that without shrinkage, and that the drying rate becomes larger with increase of the degree of shrinkage.

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An investigation has been made of the drying and shrinkage of cuttle fish muscle at zero relative humidity. Drying-time (weight loss vs. time) curve and shrinkage-time (length shortening vs. time) curve, both plotted against the square root of time, were found to be linear over a fairly wide range of time interval, which is expected from the theory developed previously. Beth curves, however, deviated from the theory at the initial stage of drying. This may be partly due to the surface condition appeared in the theory which is assumed to be kept at constant concentration in equilibrium with the ambient water vapor pressure. Experimental data for both drying and shrinkage have been analyzed in terms of the theory. It is found that, in all cases examined, the mutual diffusion coefficient for the system cuttlefish muscle + water derived from the drying experiment is slightly different from that evaluated from the shrinkage experiment.

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It was revealed by recent investigations in our country that numerous cases of food poisoning from eating of marine products are presumed to be caused by a certain species of halophilic organisms, so-called Takikawa's pathogenic halophilic bacteria. In general the causative organisms can be easily isolated from the stool of patients affected by this disease. Although the bacteria has been suspected to be of marine origin, it is very difficult to isolate them from marine products or sea water which is generally connected with causative foods. In investigating the distribution of the organisms in natural environment, use of an excellent selective medium is considered to be necessary. The authors devised, for the selective cultivation of pathogenic halophilic bacteria, a liquid medium, 5% NaCl mannitol ethyl violet broth. This medium can be prepared as follows: 5g. peptone, 3g. meat extract, 5g. mannitol, 50g. NaCl, 0.03g. bromothymol blue and 0.001g. ethyl violet are dissolved in 1, 000ml. of distilled water and the reaction of mixture is adjusted with an NaOH solution before autoclaving to pH 9.5.

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Succeeding to the previous works, in which amino acids and organic bases in the extracts of Uni were analyzed, organic acids and carbohydrates were determined on the extracts obtained from four kinds of sample with ion-exchange column chromatography, respectively.
Among organic acids, pyroglutamic acid was found ubiquitously in every sample, whereas the other acids, such as levulic, succinic, citric, lactic acids, revealed a random distribution. As the sugar of lower molecular weight, glucose was generally found together with the unknown sugar, which seemed to be a disaccharide consisting of glucose (Table 1 and Fig. 1). Both organic acids and carbohydrates occupied only a small portion of the extractives, when compared with amino acids.

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