We had the experiments on after effect of 250 D 2/6 (Upper twist: 63 and lower twist: 115 for lenght 20cm), 2/4 (Upper twist: 76, lower twist: 121) and 3/6 (Upper twist: 62, lower twist 113) amilan cords heated up to various temperature.
From this experiments the results obtained are as follows;
(1) Elongation of 250 D 2/6 amilan cord under constant tention increases the temperature-rises for high temperature than 100°C (Fig. 1.1 and Fig. 2.1).
(2) As seen in Fig. 1.2 and Fig. 2.2 inflexional points of elongation of 250 D 2/6 amilan cord due change of tension has been found about 1.5 and 3.5kg respectively. The relation between of tension and variability of elongation, as shown in Fig. 3, these curves has a minimum of variability at about 2.0kg.
(3) Tensile strength and elongation of 250 D 2/6, 3/6 and 2/4 amilan cords decrease with the temperature-rises, and variability of tensile strength increases with the temperature, but variability of elongation decreases: the tensile strength of amilan cords fells in proportion as temperature increases, and then the tensile strength of its cords has somewhat unequal, while the deviation of elongation (at break) fades.

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In the ?? revious papers, we reported about the relation between ε_D and ε_S or P and ε_S. Applying these relations for strand, we obtained the following formula regarding to the outside diameter of twine,
D=D₀(1-ε_D)-2/√3•K'D₀^-1/3E^-2/3 (P•sinθ /√3R)^2/3
where ε_D: diametral contraction of strand per unit diameter.
D₀: outside diameter of strand.
D: outside diameter of twine.
P: tension induced in strand.
R: spiral radius of strand axis.
θ: inclination of strand axis.
K': approaching modulus of strand axis by compression.
E: Young's modulus of fiber.
and the following formula regarding to the tension of twine.
P=3P•sinθ
To calculate above formulas, at first we expressed ε_s as the function of ε and θ [=tan^-1 b (1+ ?? )/2πR₀], on the assumption that R=R₀=const., and by the methods of previous papers, obtained the approximate values ε_D and P, where ^ε_s and ε are elongations of strand and twine per unit length, b is spiral pitch of strand, and zero sufix shows the each value at no load.
Hence, calculating the first formula about diameter with the above ε_D, P, θ, and R₀, weadmitted that the above formula was applied. And also in the case of calculating tension P (the second formula), the values of P and θ are to be calculated using the variable spiral radius R which is induced from the above D and D.

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The brightness of an object in a parallel beam with the intensity of light of I₀ seen from the position of the light source, can be represented by the following equation:
H=1/π•RI₀•e^-2σγ+αI₀/2σ(1-e-2σγ), (1)
where, R: index of reflection of the object,
σ: coefficient of absorption in water,
α: coefficient of scattering per unit solid angle by unit volume of water againstthe direction of the incident light,
γ: distance from the light source to the object.
In the above equation, the first term is the brightness shown by the object itself, while the second is the contribution to the brightness by the water existing between the object and the position of the eyes.
In Eq. (1) when γ=∞, the brightness shown by the water itself where there exists no object will be obtained. Then, Should it be put as H∞,
H∞=αI₀/2 ?? (2)
Consequently,
log(H-H∞)=long(RI₀/π-_H∞)-2σγ.
Therefore, it is learned that log (H-H∞) and γ are in an linearity. The coefficient of absorption σ can be obtained out of this by measuring H∞ and the brightness of the object in each distance.
Generally speaking, that an object becomes unrecognisable means the contrast between the object and the surrounding brightness becomes below η, or the threshold of the eyes. Therefore, the underwater visibility in a parallel beam is determined out of the following relationship;
H-H∞/H∞=η (3)
(However, H ?? H∞, namely, η ?? 0 against R πα/2σ)^* Visibility v, when an object in a parallel beam is seen at the position of light source, can be obtained from Eqs. (1), (2) and (3), as follows;
v=1/2σlog{(2σ/α•π•R-1)•1/η} Therefore, as for a black object that does not perfectly reflect light, putting R=0,
v ?? =1/2σlog1/η. (5)
From Eqs. (4) and (5), the following equation will be obtained as a relative equation between the visibilities of an object of R=0 and an object having an index of reflection R.
v-v ?? =1/2σlog (2σ/απ•R-1). (6)
In other words, it is seen that the visibilities of a black object is affected by coefficient of absorption alone, in the optical nature of water, and is in an inverse proportion. And, as for an object the index of reflection which is not zero, it is affected by a factor σ/α. There-fore, even in water with the same coefficient of absorption, the visibility becomes smaller as the coefficient of scatterieg α becomes larger. Also, by Eq. (6), when σ is known, out of the measurement of visibilities of an object having a fixed index of reflection and a black object, coefficient of scattering a will be obtainable, as is known.
Here, the present authors are desirous to report the coefficients of absorption and scattering that calculated from the results of measurements of the brightness and visibility of the object in a parallel beam. Also, results obtained by measuring the horizontal visibility in sea-water in the bathysphere will be explained.

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The experiments on the relations between the mouth height of the square part of the net and tension on the rope in proportion to the differences of pulling directions and current directions under various pulling velocities, have been carried out by using small trawl nets (8 HP) in Ise Bay.
From these experimen's, the following results were obtained.
1. In spite of the equal pulling velocities related to the sea-bottom, the mouth height of the square part, be pulled in the same direction as the current flows, is higher than in the opposite direction (Fig. 3, Fig. 5).
2. The tension on the rope pulled in the same direction as the current flows, is weaker than against the current while the pulling velocities related to the sea-bottom are equal (Fig. 4).
3. In the cases of the equal pulling velocities related to water, the mouth height of the square part, be pulled in the same direction as the current flows, is equal against the current (Fig.8, F ig. 10).
4. Let the mouth height of the square part and the pulling velocity related to water express by h and v respectively, when the pulling velocity is related to water, the results are following:
h∞V^-1•3 …… (indicated in Fig. 9)
h∞V^-1•3 …… (indicated in Fig. 11)

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Although it is a commonest phenomenon that a fish rushes violently when caught by a fish-hook, there does not seem to be any exact study on the strength with which such fish pulls the fishing tackle. This paper reports an experiment in which an attempt was made to measure that strength.
Fig. 1 shows the apparatus used for this measurement. When a fish catches a hook (H) and pulls the fishing tackle downward, the spring (S) is stretched and the stress is recorded by the kymograph (K).
The force with which a fish pulls the tackle downward, and the amount of work done thereby by the fish, are given respectively by (F)=c•y+r•g=ky/n+r•g and (W)={k(y/n)²+r•g•y}/2 where y is the displacement upward of the free end of the writing lever, and n, the magnification of the kymograph. c and r are the constants proper to each spring, and they can be determined from the damped oscillation brought about by hanging a known weight on the hook (Fig. 2A). The friction between the recording paper and the pen has been found to be negligible.
The measurment was carried out at the Shinmaiko Aquarium, Aichi Pref., using several species of fish reared there as the material for this study.
Kymographic records obtained by this method (Fig. 2 B, and 3 A-C) are characterized by the major peaks o ?? curring at intervals and the minor peaks that follow each major peak. Since the major peak, y, represents the maximum instantaneous force exerted by the fish, (F), and a major peak and the subsequent minor peaks are taken into account in computing (∑W), the feature of the pull can be expressed in the terms of (F), (∑W), and the time intervals of each major peak. While both (F) and (∑W) are necessary to express the strength of the pull, only (F) has been studied in some details.
In the rockfish, Sebastiscus marmoratus, the maximum of (F), (Fmax), increases nearly proportionally with the body weight (Fig. 4). Assuming this relation holds also in other spec-ies, (Fmax) per 100gr of body weight is adopted as the basis on which the forces of the instan-taneous pull in different species are compared (Table. 1).

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This study was conducted at the aquaria of Naoetsu and Hiyoriyama, and Kiyotaki Kieson Fukajo by observing the nocturnal behaviour of 20 species of fishes and by comparing it with the day-time behaviour. The gist of the results is as follows:
(1) Fishes can be classified into 3 groups: fishes which move only in the night-time, only in the day-time and fishes which move at night as well as in the day-time.
(2) The behaviour of fishes in the night-time can be said to be principally due to the activities for feeding.
(3) Most of the coastal fishes move only in the night-time and they behave somewhat more lively in the night-time than in the day-time.
(4) Nijimasu Salmo irideus (Gibbons) was ascertained to be inactive in the night-time.

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“Masu-ami” is a common type of trap nets for use in shallow wate: fisheries in Japan. The net is constructed with three main parts, a lead net, fence and bags, as shown in Fig. 1. In general practice three or more bags are placed at different position of the fence. Fishermen haul the bags once or twice a day to capture the fish which have entered in to them.
The purpose of the present study is to examine fishing efficiency of the bags which may vary depending upon their positions in the net and thread materials used for the bags. A factor as to whether or not the bags have been dressed with a dye may also have different effect upon the catch. For this reason series of experiments were carried out at two fishing grounds in Ka-nagawa Prefecture during the periods of May to December 1951, and March to November 1952, using from three to five bags per set for a test as shown in Figs. 3-5.
Each of the bags was made of different materials of thread such as nylon, vinylon andcotton which were either dyed or not dyed. From the results indicated in Tables 1-4 and Figs. 6-9, we may assert the following:
1. If all the bags of a net were made of the same kind of a thread material and a dressing dye, the catching ratio of each bag is nearly constant in accordance with their respective position in the net throught a period of the test.
The catching ratio by position may be summarized as follows: i) The net at Ottomo, May 17 to December 27, 1951 Position of Bags I II III IV
Catching Ratio (S%) 11 39 39 11
ii) The net at Natsushima, June 9 to November 25, 1951 Position of Bags I II III
Catching Ratio (S%) 14 31 55
iii) The net at Natsushima, March 9 to November 11, 1952 Position of Bags I II IV V
Catching Ratio (S%) 18 32 32 18
S%: Strength of selective action of the fish for a bag position calculated by dividingthe catch of a bag at a position by the total catch of the net.
No bag used at the position III.
2. When the bags, each made of a different material and dressing, were used together in the same net, a nylon bag dyed in blue was found more efficient than any other bags. Both the bags of non-dyed nylon and of the one dyed with cutch followed the blue nylon bag in their efficiency. The bags made of either vinylon or cotton had good catch, too. However, when dyed with cutch, they were-not so effective as the ones used without being dyed. The cotton bag dressed with coal tar had the poorest catch among them. This conlusion has been drawn on the basis of the following calculation and comparision.
Let S represent the strength of selective action of the fish for a position of a bag, and E the strength of selective action of the fish for a kind (thread material and dressing) of a bag. Then the strength of a bag at a position prepared in a certain kind may be expressed by SE. As the value of S corresponding to a bag at a position has been determined as above, the value of SE will be obtained from experiments (Figs. 8-9). Take the test 5 in Fig. 8 for example.
S_IE_V=14.3 S_VE_V=8.6 S_I=S_V=18 ∴ 18E_V+18E_V-14.3+8.6 ∴ E_V=0.64 S_IIE_A=28.6 S_IVE_A=48.5 S_II=S_IV=32 ∴ 32E_A+32E_A=28.6+48.5 ∴ E_A=1.24 Accordingly E_V:E_A=0.64:1.24 ?? 1:2
Here S_I to S_V denote the strength of selective action of a bag when placed at the positions I to ∇ ; and E_V, E_A the selective strength of a bag made of vinylon or nylon respectively.
Table 6 and Fig.

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As regards the flactuation of catches, there are few examples of the discussions about the causes of this fluctuation throngh the view of the diffusive movements of fish schools, although many examples of the discussions about the statistic dealing of the fluctuable results.
The author attended to explain, this fluctuation by means of the combination of the movements and tha appearances of fish schools.
In the result, it is said that soon after beginning of catch the maximum abundant one appears and then successively the gradually scarce ones continue till the last of one period of catching.

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This article presents a method of estimating mortality and growth parameters of a biological population through observed changes of the size composition, whether truncated or not. The principle is the least squares adjustment of data with estimation of parameters involved in the condition equations. A little complication comes out from the facts that the sample composition must be regarded as a vector variate, and that only some of the components are constrained to each condition equation. Though a little laborious in numerical calculation, it will especially meet such a situation where recruitment by growth is occurring and technically difficult for direct estimation. The number and combinations of the independently inferable parameters are considered, with which applicability is indicated to be generalized by adopting an appropriate division of size or time interval in advance. And a numerical example on a benthic larval population was discussed briefly for explanation and some interesting scopes of extrapolation are suggested.

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The logistic law of growth have been generalised and a number of the growth curves were obtained. One of them was coincide with the G_OMPERTZ law of mortality which was applied by W_INSOR as the growth curve. Moreover a system of growth curve which correspond to the law of M_AKEHAM was obtained. Details of the results will be published in the Journal of Tokyo University of Fisheries.

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The variance of the simple estimates of the number belonging to a certain body length class is rather large and is composed of three components, i.e., between-day variance, between boat one and within boat one. As an example, the drift net fisheries of Japanese Sardine was taken. The second and the third one are at their maximum near the modes of body length composition, while at their tails they are comparatively low.
When we use the ratio estimation in order to separate the variance which dues to the variation of the size of shoals from that due to the heterogenuity within the shoals, we find that the correlation coefficients between the total catch of a sample boat and that in a certain length class are, in generally, largest at the modes of the body length compositions, while at the larger tails, they are low. This fact is considered to be caused because the main year class and the younger ones build up shoals with the individuals of the same size, while the older ones migrate independently.

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The author reported in the previous paper that total weight of catch except that of shells and weeds from various bays of Japan was proportional to annual average quantity of suspensoid in the water of the bay.
Accordingly, it is disirable for fisheries economics to have a fish population in the bay of such composition as to be expected to give the most valuable products, since the weight of catch in total is controlled by the condition of the bay. Here the species in the catches in 1949 from various bays in Japan are grouped into three trophic categories, plankton-feeder (2nd consumer which feeds on producer the plants and 1st consumer) benthos-eater (3rd consumer) and pisci-predator (from 3rd or 4th to higher consumer). And a equation.
C=2+7.3K+27K²
is obtained, where C is percentage fraction in weight of the 3rd group and K=Cl₀•D•B/10000 (Cl₀ is annual average of Cl‰ in the surface layer of the bay, D the average depth in m. and B the breadth in km. of the mouth of it). The more oceanic character has a bay, the more increases the C-value until it attains to Ca. 30 the value for all coastal fisheries in Japanr in 1949. While this value for past 35 years varies from 11 to 33 as shown in Fig. 2, where it is comparedd with the results studied by H. S. S_WINGLE on the populations in 88 fertilized ponds in Alabama, United States, though the correlation between those in sea and fresh-weter ponds is not clear.
The effect of change in C-value in outside water upon that in bay, and the cause of such change in the sea are left for future study.

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In the mean number of vertebrae and lateral-line scales, the salmon of the main river and a tributary, Toyohira River fairly exceed those of another tributary, Chitose River: and the the mean number of vertebrae of the fry of naturally reared populations in the main river is more than that of the fry which were produced in the hatcheries (Chitose and Otoe).
Without regard to the effect of any factor, the salmon of Ishikari River System constitute two populations at least, which are different from each other, and so, evidence available indicates that the mature salmon mostly ascend the home river in which they were yielded, during their spawning migration.

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From the result of the researches for the stomach contents of the tunas and marlins, which have been carried out from March 1949, considerable number ofthe juveniles of tunas, marlins and swordfish are found. Of these juveniles, skipjacks of the length 70-450mm are the most abundant ones. On the bases of these juvenile skipjasks, the following ithems are treated.
i) Seasonal and local appearance.
ii) Local size-compositions and their seasonal variations.
iii) Description of the characters on these specimens which are not much digested.
Within the limit of the investigations, which were taken place in the adjacent seas of the South Sea Islands, the Bonin and the Midway island, these juveniles appear without distinction of the seasons and the localities. The abundance and the size-composition of these juveniles, seem to differ remarkably according to the differences of the seasons and the localities. Such differences are considered by the author, to have close relation to the subtropical convergence. Furthrmore, cosidering from size-composition and locality of their appearance, the author hypothesizes that the skipjack spawns in the vast areas of the tropical and subtropical seas, not by any means in a short period.

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An end-cylinder as shown in Fig. I. B was devised on the haul net to collect young fishes. They, entering into the net, are gathered around the median tube alive and being free from mutilation even when the net is lifted up.
To observe the details of the samples, staining with the dyes Cyanine 5 R or First Flack 8B is found to give a much better condition than the cases with any other staining materials as shown in Table I.

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The morphological variations dependent on the species, sex, and growth stages are researched in three approximate species of the family Hoplichthyidae (Hoplichthys gilberti J_ORDAN and R_ICHARDSON, H. langsdorfii C_UVIER and V_ALENCIENNES and H. fiiamentosus M_ATSUBARA and O_CHIAI).
In this research, the auther particularly remarked the following body parts: trunk length, dorsal spine length, dorsal soft ray length and pectoral fin length, which are all distinctly variable with species, sex, and growth stages.
The results obtained are summalized as follows (Table 1).
1. The sexal dimorphism displays in all Hoplichthys in the same characters, such as trunk length, dorsal first spine length and dorsal first soft ray length.
2. There appears the tendency toward parallelism in the observed differences between sexes and also between growth stages, among all species through these characters.
3. The morphological differences dependent on sexes and growth stages run parallelld with those between two species, H. gilberti and H. filamentosus. H. gilberti differs from H. fiiamentosus in the same way that the male differs from female, or the old from the young. But these parallelism can not be found between H. gilberti and H. langsdorfii, nor between H. langs-dorfii and H. fiiamentosus. 4. The specific differences are shown in the elongate conditions of dorsal soft rays of the male fishes which begin to mature (Fig. 6). H. gilberti diverges into two types in characters of soft dorsal fin. In one type, which is called herein as type A, the fourth to seventh soft rays are filamentous, whereas eighth to fourteenth are not longer than the first ray. The other type, which is called type B, is characterized by the length of second to thirteenth or fourteenth soft rays, which are longer than the first ray. In H. langsdorfii some anterior soft rays are filamentous and eighth to fourteenth rays are longer than the first ray. In H. filamentosus. all dorsal soft rays are filamentous, which is the peak of the differentiation of this character. The pattern of these processes in differentiation is shown in Fig. 7.

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The Hyuga Nada (Hyuga High Sea) when taken in wide sense extends off the eastern and east-southern coasts of Kyushu Island, viz., from up north the Bungo Strait down to south the Osumi Penninsula, and abounds, amoungst others, in red gurnards, of which economically important are the following five species; Chelidonichthys kumu, Pachytrigla alata, Lepido-trigla japonicus, L, güntheri and L, microptera. Examination of their stomach contents reveal that they devour by far Crustaceans and those small fishes as hidden in sand-mud or crawling on sea bottom (Table 2). Voracious as they are, their stomach was often found stuffed with food, which weighed 3-4% of the body at maximum. Table 3 and Fig. 1, A-F give the results of the statistical observation of their egg. Ova measuring over 1.0mm in diameter are characterized by having one or three oil globules and almost complete transparency and were taken as mature eggs. The degree of maturity was defined by ratio of mature ova to the whole ovary in weight and is given in Table 6. Single mature ovum weighs about 0.0011gr in Chelidonichthys kumu and about 0.00095gr in Pachytigla alata. Number of ova to be liberated at first spawning is estimated 10, 000-25, 000 in C, kumu, and 2, 000-3, 500 in P, alata.

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Regular monthly observations as well as those conducted at irregular intervals from 1949 to 1952 inclusive show that the spawning period of sardine and round herring covers November to next April but that of Anchovy extends all year round along the coast of Miyazaki Prefecture. Frequency distribution of ovarian egg diameter of sardine and round herring was found unimo. dal in samples obtained from June to October. But ovary weight of these fishes increase rapidly in November or December when frequency distribution of ovarian egg diameter assumes bimodal or trimodal when examined as before. Anchovy stand also quite different from the other two in ovarian weight and egg diameter, i.e., no precise period of rapid increase of ovary was not found and egg diameter distribution always differs in individuals even taken at the same time and locality.

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The observation were made for the young Alaska pollack caught by small trawlers in Funka-wan Bay and setting net in the waters around Hokkaido.
1) The growth rate of 0-1 age fish of Funka-wan Bay seems to be not variable for the season.
2) The vertebrae number of the fish in Funka-wan Bay havemarked variations between the two year classes and neighbouring regions.
3) Some considerations were made for the population structure of Alaska pollack by the present and past data.

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As shown in Fig. 1, the spines on the dorsal surface of the Japanese topshell, Turbo cornutus, a-e usually divided into four types according to their position. In June 1949 the writer liberated 258 topshells into an artificial pool 15m×7m wide in Kominato Marine Biological Laboratory, Chiba prefecture. Here the environment, from the standpoint of salinity, current, bottom. character and available food, was not as suitable for this species as was its natural habitat. In June 1950, 58 specimens were recollected from the pool. Observing their spines, it was found that peculiar changes had occurred during the year of transplantation into the artificial pool, asshown in Tables I and 2. The groups produced shell spines that lower in position (A→B, A→C. and O→C) are proved to be superior in increased weight and length of shell (Tables 3 and 4). nes, the upper spine being related to excurrent action, the lower to incurrent action. Anatomical observations on this snail (Fig. 2) and on the parasitic gastropod, Amalthea conica (Table 5). bear out this conclusion.

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The review of the works conducted in the past has brought the conclusions as follows on the recapture of tagged fish as well as course and season of migration for Japanese mackerel.
1. In the Sea of Japan, the rate of recapture was found to be 0.92% against the number of liberation for Japanese islands, whereas it was 0.51% for the eastern coast of Korea. In the pacific coast of Japanese islands, the same rate was 0.80%. These figures indicate very low rate of recapture compared to those obtained for yellowtail.
2. The number of recapure show peak figures during 41 to 50 days after the release, but they are very low immediately after the liberation. Considerable number of tagged fish were also caught as late as one to two years after the release.
3. n (the number of recapture) and t (the elapsion of days after the release) may be expressed by an exponential equation. (Fig. 2),
n=5×10^-0.0017t.
The same equation was calculated for yellowtail as n=10×10^-0.0017t
4. The route of migratiou may be summarized as follows:
(i) The shoals migrating southward along Korean coast in fall arrive Korean Strait, thence the fish, in spring and summer of the following year, enter northward migration but in two split shoals, the one along Korean eastern coast and the other along the northern shcre of Japanese islands.
(ii) There seems, to be a “fish way” connecting the west side of Oki Island and Kogendo, Korea, which is observed in the months of May to September.
(iii) The study also indicates the existence of another “fish way” which, seen in summer months, runs from Yamato Bank in central part of Sea of Japan to Kankyôhokudô, Korea.
(iv) The mackerel in Sea of Japan show both north-and southward migration within a year, but there is a tendency that the fish of older ages have center of their migration in southern waters within range of moving.

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1) Several low temperature regions, which play big roll in fisheries, were found in the Sea of Japan during the simultaneous observation conducted in the summer (late July to early August) of 1591. This paper deals with the oceanographic character and the year-to-year shifting of the locations of these regions, especially the one located off Sado Island.
2) The results of the above observation indicate that within the low temperature region off Sado Island the water had the intermediate character between the water cold and the warm ocean currents distribution in the adjacent areas, and that the surface water of the cold current from the north was laterally mixing in this region with the subsurface water of the warm Tsushima Current from the south. As the bottom water of the Sea of Japan has been considered the mixture of these two waters, this region may be said to be one of those regions where the surface water of the cold current is converted into that bottom water. In that it is caused by the lateral mixing of two currents, this low temperature region differs from other similar regions in the Sea of Japan or off Kii Peninsula which are caused by the upwelling of the deep water.
3) Owing to the presence of this mixing region, the subsurface water of the Tsushima Current is deprived of much of its original properties in the north of Noto peninsula.
4) The location and the degree of development of this mixing region depend on the fluctuating strengths of the cold and the warm currents, and therefore are subject to considerable seasonal and annual variations. There are some indictions that it is best developed in spring.

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Theoretical treatment of the distribution and seasonal changes in the contents of nitrogen and phosphorus have generally been limited to the case of oceanic water. The similar treatment, however, is difficult in the case of coastal water. The difficulties may probably be due to the facts that the coastal water is rich in or-ganic matter and that a condiderable part of it is in the form of dissolved organic substances.
Some explanations on the seasonal changes in the contents of nutrient salts in Tokyo Bay have been forwarded from the results that the nitrogen phosphorus ratio in such waters was found to be the same as that in oceanic water

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Many springs and flowing wells are distributed in northern vicinity of Odawara. City, Kanagawa Prefecture. Throughout the four seasons, clear ground water is continually flowing out of every well and spring, supplying for domestic and industrial ?? urpose.
Although the waters of this district are considered to be of good quality in their chemical properties, curious to say, fishes can hardly be kept alive in these waters. Fishes, when put into these waters just flowed out, soon fall in an unhealthy condition and can not survive long.
Gas contents were examined. Sufficient quantity of oxygen for the life of fish was proved to be dissolved in these waters, but nitrogen gas contents indicated abnormally high supersaturations.
After some experiments, we reached to the conclusion that the death of fishes in these waters must have been brought about by so-called “gas-disease” caused by the abnormally high supersatuation of the nitrogen dissolved in the ground water. Experiments also teach us that the supersaturation values of the nitrogen above 130% in the water are fatal to fishes.
The gas-disease of fish is considered pathologically to be similar to the caison-disease and the diver-disease of man and give us many interesting and important problems for scientific investigation both from theoretical and applied point of view. E_GUSA. one of the authors, is now studying the subjects and the results of which will be reported in near future.
In this report we will confine ourselves in the quantitative determination of the nitrogen gas in the flowing water of the distict. The summary is as follows:
1.) The flowing water of all of the fifteen artesian wells and two springs we visited and investigated showed the supersaturation of nitrogen gas. The values obtained ranged from 118 to 159%, but were mostly above 140% (Fig. 1. and Table 1.).
2.) It was observed that each well and spring has its specific supersaturation values of nitrogen stationary for a long period. The oxygen contents showed greater fluctuations compared with those of nitrogen (Table 3, 4 and 5.).
3.) Two artesian wells, the waters of which were also known to induce the gas-disease upon fishes, were found in other districts and their waters were investigated. Both wells showed very high supersturations of nitrogen (146 and 161%), but very low values of dissolved oxygen (below 10%) (Table 2.).

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Being the very unstable substance, sulphide in bottom deposit have to be determined immediately after sampling to obtain the accurate value. It is necessary to try proper fixative procedure, because the determination of sulphide cannot perform at the researching place.
In this paper the auther examined on the change after sampling in sulphide in bottom deposit and its preventive methods. The results obtained are as follows:
1. Sulpbide in bottom deposit on exposing to air decreases gradually, and it closed with water increases.
2. The change in sulphide, in bottom deposit closed with water decreases according to the lowering of temperature and does not change entirely at 2°C.
3. When about 2% of sterilizers such as 50% NaOH, saturated solution of HgCl₂ and toluene are added to the bottom deposit closed with water, the change in sulphide is prevented completely.

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The authors have studied on the abnormal mortality of hunging oyster in the sea of Nakami from the view point of physioal chemistry, and the results are summerised as follows.
1) The water of Nakami is of two layers with the upper of lower salinity, and thus shows a very high vertical stability. Into the distinct discontinuous layer, which develops between them, are supposed to be adsorbed some surface active substances resulting any change of surface tension.
2) Our observation shows, that is the case, and the active substances are hydrogen-and other sulfide and organic matters, and that they were abundant in summer and selectively absorbed into the layer.
3) The greatest damage on oyster seems to take place within the moving range of this discontinuous layer and consequently the surface active substances are supposed to have something to do with the abnormal oyster mortality.
4) The fact that hunging oysters suffered from death to the greatest degree during the period of turbulence of water caused by typhoon or during that of “red-water” in autumn, is explained by dissolution of the injurious substances from submarine deposits and by defusion of the surface active substances of the discontinuous layer into the sea water around.

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Various authors have worked on the cause or causes of unusual mortality observed during summer in the Japanese oyster, Ostrea gigas, with the following results:-
(1) Proof against such an unusual event are those culture-beds which enjoy an appropriate water condition ensuing from either (a) the temperature being below 24°C coupled with the salinity ranging 33-34‰, or (b) the temperature somewhat higher (26°-36°C) but the salinity slightly lower (30-32‰) than the former.
(2) The summer conditions of water consequent upon higher temperature (26°-32°C) and salinity (33-35‰) were found in Moroiso Bay decidedly fatal to the profusely egg-laden oysters which however rather gradually succumed to death.
(3) Spawning was followed by sudden fate at Kanazawa and Akamizu during a period from late August to early September in those oysters which had been previously exposed in summer months to a temperature above 26°C and at the same time to a salinity of 32-34‰, although the water conditions were taking a favorable turn for them while dying. (These three items were verified by Seno, Fujimori, Kusakabe, and Yokota).
(4) Transplanted anywhere else from Shimizu Bay as it was, the Shimizu stock of oysters still maintained its regular spawning season of mid-autumn irrespective of conditions of life, of its new habitat, briskly continuing its existence during the afore-mentioned critical period amidst all other dying native ones. Hence the mortality of the latter dependent on coincidence of spawning season with the time of upturned temperature and salinity (Seno, Fujimori, and Kusakabe).
(5) Nothing suggestive of contagion could be detected in the perishing oysters (Seno, Kusakabe, and Miyazaki); nor harmful bacteria in them (Orton).
(6) Autolysis products of ovary of an oyster induced “gaping” condition in another otherwise healthy one when injected in its visceral mass (Yokota, ).
(7) The higher temperature and salinity of water markedly lessened reproductirvity of diatoms (Yokota) which were found indispensable food for rearing Olympia oyster lavae (Hori).
(8) Gaping oysters were found to have their digestive diverticula rediced in size and faded in color.
It may be mentioned a measure was taken by Yokota, Inoue, and Sawto with a view to reducing the unusual mortality of the oyster in summer. Of injections of Vitamin B₂, KI, KCl, KIO ??, diatom extract crone of them, a certain dose of KI appeared to answer the purpose (Preliminary Report of Experiment to Reduce Mortality of Oyster in Summer 1950. B_ULL. J_AP. S_CO. S_CI. F_ISH. V_OL. 15 No. 9.)
The premnt paper deals with an account of further studies conducted in summer of 1948 and 1950 on the same subject, and the attention of the reader is called to the accompanying Tables I and II which tabulate the results of experiments, Tables III and IV which give a summary of environmental conditions of Akamizu oyster farm under consideration, and Table V which sums up mortality of oysters. Remarkably enough, shots of KI solutions were likely to reduce the mortality in summer even under adverse conditions resulting from unsuitable temperarure and salinity and also shortage of food. Such effects of KI and other already mentioned related facts when taken together appear to point to the conclusion that unusual deathrate ensues from accumulation of harmful autolysis products due to disturbed metabolism which was given rise to by persistence of higher temperature and salinity of water during the spawning season. A large dose of KI is therefore recommended to be administered to the oysters when they are spawning in summer.

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The spores of several algae (4 spp. in Chlorophyceae, 3 spp. in Phaeophyceae and 3 spp. in Rhodophyceae) were cultured in the laboratory under those different light-condions as follows:
1. Concerning to the light intensity; A) in full sunlight through a window glass, avoiding the direct rays, B) under a shade of one sheet of white cotton-cloth, C) under a shade of three thicknesses of white cotton cloth.
2. Concerning to the quality of light; under a colour filter using the solution of red, brown, yellow, green, blue, and violet colour pigments.
3. Concerning to the duration of light; A) long-day, 24 hours, B) normal-day, 10-12 hours, C) short-day, 8 hours.
Results, shown in 1-5 tables, might be summarized as follows: a) When kept in darkness, the spores of green algae did never germinate nor grow into two-celled sporelings for more than 1.5 years, while most spores of brown-or red-algae did slowly germinate. In decreased light, the growth of sporelings of green algae were greatly retarded, while those of brown-or red-algae were rather accelerated. But one exception in green algae was observed, i.e. the sporelings of Monostroma grew more slowly in decreased light (B-condion) for about two weeks after germination, but there-after they set in faster growth then in full sunlight.
b) The sporelings of green algae grew more rapidly under yellow, red, or blue light than under brown or green light.
c) The spores of Enteromorpha germinated and developed more rapididly in the long-day condition. With Monostroma, however, the germination and development in the earlier stage were faster in the normal-day condittion, but after a while, more rapid growth and richer formation of spores were reversly found in the short-day condition.

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S_UTO (1950), in his interesting studies of spores of Gelidium and other algae, pointed out that “Shedding of Gelidium occurs daily in the afternoon, and such periodicily in shedding is seen in many species.”
In present study, the shedding of Gelidium Amansii L_MX. has been investigated during the past three years at Yoshimi, Yamaguchi Pref., Japan. The results are as follows:
The shedding of this species occurs daily within a few hours as mentioned above, but the shedding time of carpospores is earlier and shorter than that of tetraspores (Fig. 1). And then the shedding time in either kind of the spores changes gradually with the advancement of seasons-from June till November-, as shown in Fig. 2.

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The antibiotic sardine oil, which was prepared by adding M/10 Cu-stearate or by blowing oxygen at 100°C in the presence of M/100 Co-stearate or m-nitroaniline to the oil, was utilized in the treatment of netting cord.
Some effects on the preservation were recognized (Fig. 1, 2), but further studies on the dilution reagents of dye and on the drying of net are required to obtain satisfactory result.

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The microbiological deterioration of fishing nets during storage was preliminarily studied.
1) After periods of from three to six months' storage under dry conditions, textile fibres of fishing nets were found to be covered with a large number of survived cells of aerobic cellulose-decomposing bacteria of marine origin. These findings suggest an important role played by marine cellulose-decomposing bacteria in deterioration of textile fibres during storage.
2) Fourteen strains of marine aerobic cellulose-decomposing bacteria were purely isolated from the fishing nets which had been stored, under dry conditions, for three months after fishing. These isolated bacteria were classified into a new species of myxobacteria, viz., Cytophaga haloflava after detailed taxonomical studies.

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By the paper chromatography, we found that the water extracts of Digenia simplex Ag. contained a certain organic acid. We obtained this acid as the sodium salt, and isolated the free acid from this salt by means of ion-exchange resin.
The sodium salt of this acid was identified by the rotation measurement, hydrolysis and elementary analysis as scdinm α-(α-D-mannostdo)-D-glycerate. By C_RIEGEE's reaction, it was confirmed that mannose combined with α-hydroxyl of glyceric acid in this substance.
From the results of pharmacological experiments with 0.1% aqueous solution of sodium α-(α-D-mannosido)-D-glycerate against Ascaris lumbrcorldes, it was found that Ascaris lumb. showed a characteristic struggling motion to escape.

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Postmortem changes of acid-soluble phosphorus compounds of fish muscle were studied to know how the immediate treatments after its catch have effects upon the glycolysis.
Frigate mackerels, Auxis tapeinosoma (Bleeker), caught by angling were divided into two different killing groups: the one was instant death which was killed cutting head off immediately after the catch, and the other death in agony which was dead after struggling for several minutes in the sea-water pool at the bottom of fishing boat.
As shown in table 1, remarkable differences of acid-soluble phosphorus compounds were recognized between the fish muscle of instant death and death in agony.
For example, the quantity of true inorganic P increased only slightly in the muscle of instant death, but did almost as twice as original amount in four hours after death in the muscle of death in agony.
On the contrary, the quantity of adenosine triphosphate in the muscle of death in agony, decreased very rapidly disappeared within four hours after death, and it was recognized to enter into full rigor.
Moreover, the quantity of both adenylic and inosinic acid which was derived from the breakdown of the former, increased rapidly in this muscle, so the reason why more ammonia yielded in the fish muscle of death in agony than in instant death was considered to depend upon deamination or glutamine immediatly after the catch and desamination of adenylic acid during the autolytic process.

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Generally, the reduction of trimethylamine oxide in fish muscle is believed only due to the bacterial agents, and the trimethylamine level provides the best indication of bacterial deterioration in marine fish muscle. This experiment revealed that relatively large amount of free trimethylamine was contained in the dark muscle of pelagic fish, such as albacore (Germo alalunga (G.)) or frigate-mackerel (Auxis tapeinosoma (Bleeker)), tested immediately after catch and that marked increase in the amount of this amine was observed even under aseptic condition. On the other hand, no appreciable amount of trimethylamine was produced in the white muscle of these fish under the same condition.
Trimethylamine oxide, when added to the dark muscle tissue, was reduced to corresponding amine during aseptic incubation, but no reduction occurred when added to the white muscle. Trimethylamine oxide reducing ability was storongy diminished or inhibited when treated with heat or added with dipyridyl or potassium cyanide as inhibitor which is known to have strong inhibitory influence on the enzyme with heavy metal atoms, especially iron.
Despite the treatment with heat, a slight reduction was noted in the case of dark muscle; this might be caused by the thermostable and automatic reducing system contained in the tissue.
These results obtained suggest the existence of certain biological system somewhat like the trimethylamine oxide-reductase present in certain bacteria.

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The authors determined the general chemical components of the skipper, using four samples caught at different times in the fishing season of 1951. Determinations were separately made on three groups classified by body length. (A<B<C).
The results obtained were as follows.
1 The fat index and the crude fat content of skipper were higher in fishes with larger body length, and they became lower toward the end of the fishing season.
2 The content of crude fat was inversely proportionate to the moisture content, and their sum remained constant, at about 80% of meat weight.
3 Crude protein content was fairly constant, in all samples regardless of boby length and fishing season.
4 Crude ash content in the head, bones and fins increased with the body length of fish.
5 The average values of chemical components in B group fishes which occupied the main part of the catches in 1951 were as follows.
Moisture 65.56% Crude fat 14.32%
Crude protein 19.90% Crude ash 1.54%

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In the previous report, authors found that among general components, the crude fat and moisture contents of meat varied with the size of fish and fishing seasons. In this report, de-terminations were made on nine skipper samples caught at different times in the fishing season of Augast to December of 1952. The fishes were divided into three groups by body length (a<b<C), and some of them were then subdivided into two groups by fat index (d<e).
The results were as follows.
1. The fat index and the crude fat content of skipper meat in 1952 were lower than that of 1951. The correlation coefficient between the fat index and the body length was +0.56.
2. From the sum of the moisture and crude fat contents, the skipper samples in 1952 were clearly didided into two groups. One group, which was caught before November 20th, had an average value of 79.77%, with the standard deviation of 0.91, while the other group, which wa caught after November 20th, had an average value of 77.07%, with the standard deviation of 0.69. The correlation coefficient between the crude fat and the moisture content was -0.94.
3. The correlation coefficient between the crude fat content and the body length was +0.72, and that between the crude fat content and the fat index was +0.70. The crude fat content became less toward the end of the fishing season.
4. From the data in this report as well as those in the previous one, the calorie value of the whole and the edible portion of skipper were calculated, and a some discussions were given about the calorie values of the fish in relation to its size, fishing season and year of catch.

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The seasonal variations of the liver weight, oil content, and vitamin-A unite of the Mackerel caught in T_AJIMA was observed.
1) Both the liver weight and oil content were affected by the nutrition of the kind of the feed and physiological influence of the reproduction.
2) The liver weight of the female was very increased in time of the period of egg-formation and rapidly consumed by the spawning, but in the male the liver weight does not change so remarkablly.
3) In February, the low unite of V-A was shown in spite of the low content of liver oil, that is seemed by the effect of the difference of feed.

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Accumulation of vitamin A-the growth promoting vitamin-in the liver is very little in early stage of growth, while it will suddenly be accumulated in the liver of the shark when it has grown to adult (above 80cm in body-length) (Fig. 1).
The ratio of vitamin A concentration above 10 C. L. O. U. to whole individuals in each body-length-may be called the group accumulative ratio of vitamin A-were calculated and were graphically shown in Table 1 and Fig. 2.
The estimation of the age of shark will be depended only on the body-length, because shark has no annual rings on scales or ear stones.
The author has made the deduction of the age of a shark (Squalus suckleyi) from the frequency curves of the body-length by using the samples of the ONAHAMA, the NIPPON-KAI and the HOKKAIDO-TOHOKU Sea region, surrounding Japan Islands (Fig. 3). From the results of these treatments, it was presumed that the shark grows about 15-25cm a year. The re-lation of age and body-length as being shown in Table 2. At two age it reaches the economical minimum body-length (60-70cm), while the first parturition age is attained at three age (85-95cm in females and 65-70cm in males).
It may, therefore be, said that the group accumulative ratio of vitamin A in the shark is rapicl1y increased at three age in which the gonads have been ripened both males and females.

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The oils contained in the fresh liver of the dogfish, Squalus suckleyi, could be extracted in several fractions by applying the processes of freezing, autolysis and alkali-digestion.
When the Iiver was once frozen and then autolyzed for several hours at a normal temperature the greater part of the oil in the liver was easily released, but the vitamin A potency of the oil was lower than that of the oil which was extracted by digesting the whole liver with alkali.
The oil removed from the liver-residue was small in its amounts, but the potency of vitamin A was very high.
As vitamin A content in the liver-residue was gradually raised with the increase of the oil released from the liver, the high vitamin A potency oil could be extracted even from the low vitamin A content liver.

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In the previous papers^* we reported that fish oils, when slightly polymerized, become highly nutrious more than the original ones. In case of oils from the fin whale, Balaenoptera physalus, and the arrow toothed halibut, Atheresthes evermanni, the nutritive value of the slightly polymerized oils were found higher than that of soybean oil.
The present paper deals with a research we have made on the properties of polymerized or oxidized oils processed by various methods in order to prepare marine animal oil into edible oils. The results are summarized as follows:
1. Properties of the polymerized oils differ according to the conditions of polymerization (see Tables 1 and 2).
2. Viscosity of the polymerized oil prepared by using acid clay as catalyst is comparatively low, but when AlCl₃ is used as catalyst, the oil is highly viscous (see Table 3).
3. Mean molecular weight of mixed fatty acids of polymerized oil prepared by using acid clay as catalyst is lower than that of the fatty acids of the oil catalyzed by AlCl₃.
4. A polymerized oil good for edible purpose should not be too viscous. In other words, it is desirable to keep viscosity of the oil under 300 (Redwood 38°C). According to our observation, viscosity index of the polymerized oils rises higher than that of the original oil when the polymerization proceeds to a certain extent (see Tables 4 and 5).
5. When the oil is polymerized to some extent, the yield of polybromide from mixed fatty acids decreases distinctly. In order to compare the iodine value and mean molecular weight of the unsaturated acids with these of mixed fatty acids of the original oil, ether or benzene insoluble bromides which were gained from mixed fatty acids of the polymerized oil were debrominated. The comparison revealed that the iodine value of the unsaturated acid thus obtained is lower than that of mixed fatty acids. While, the mean molecular weight of the former is greater than that of the latter (see Table 15).
On the basis of our experimental results we assumed that the polymerized oils fit for edible purpose are those which are low in viscosity and small in molecular weight. For this reason polymerization must be carried out by using a suitable catalyst such as acid clay when marine animal oils are processed into edible oil.

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Taking into account facts that the catalase activity of the washing of the surface was fa ?? greater than that of the inner part and became nil on boiling for five minutes, it is clear tha ?? the activity originates from micro-organisms developed over the surface. So, the catalase activity at any suface of “Kamaboko” will give an index for degree of loading with microorganisms.
The present data show that the freshness of “Kamaboko” can definitely be estimated by the action of the catalase activity determined on a 5cc portion of washing of its surface with 250cc water using a tooth brush. A mancmetric procedure has been described.

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