In order to make acertain the difference of the shapes at the opening of cod ends afect to what extent upon the resistance, the author made some considerations upon the theoretical relalion between the resistance of the pyramid type cod end, RS_n/(KS²) and the shape of its opening, a/b (Eq. III-6 and -7). Where R is the total resistance of the cod end, K the resistance of the unite area of the netting fixed perpendicularly to a stream, S_n the total area of Webbing, S the area at the opening and a/b the ratio of the height and the width at the opening.
Further, the author made a series of model experiments of four kinds of cod ends of which the value a/b are changed 1.00, 0.68, 0.50 and 0.35. Thus he compared the actually observed values with the theoretical ones and obtained the results shown in Fig. 13.
From this figure, it is found that the coincidence of the observed value of the resistance of the net with its theoretical value is satisfactory and its resistance is nearly constant within the limit of practical shape.

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The previous report¹⁾ has proved that coefficient of plane net resistance against vertical flow of water is different in accordance with forms of knots. In the present study an experiment has been carried out for finding differences in coefficient of the resistance among sample nets of various kinds of fibers. Of the nets used for experiment some were made of natural fibers such as cotton, manila twine, and straw rope, the others were of synthetic fibers including Amilan (polyamid), Tevilon (vinyle chloride), Silklon (polyvinyle alcohol), Cremona (polyvinyle alcohol), Kurehalon (vinylidene chloride) and Saran (vinylidene chloride). Most of them had trawler knot with the specifications as shown in table 1.
The net was stretched on a frame, 1×1 meters, of alminum bar, 0.6 centimeter in diameter, with shrinkage of 30 per cent so as to let each of meshes form a square. Towing tests for hydraulic resistance of the net were carried out at the rate of 4 to 40cm/sec., the experimental facilities being described previously. The coefficient of net resistance was calculated from the formula R=kv² as same as performed in the preceding study, where R is the resistance of a net piece (gr.) and v the towing speed (cm/sec. ). In this case, k becomes nearly constant when the value of Reynold's number (v•d/v) is greater than 3×102 (Fig. 1), where d is the diameter of the netting cord (cm.) and v the kenematic coefficient of viscosity (cm²/sec.).
Thus, the relationships between k and d/l in different kinds of fibers are shown in Fig. 2, where l is the mesh size (cm.). As is obvious in the figure the value of k is larger in natural fibers than in synthetic fibers with considerable differences even between synthetic fibers. It is interesting to observe the net made of cut-fiber of polyvinyle shows the value of k higher than that of the net made of endless fiber of polyamid, vinyle chloride and vinylidene chloride. From these results it may be concluded that the value of k is greatly affected by roughness en the surface of nettingg cord.

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Fishing nets, when set under a current of waters, are liable to deformation. Since the synthetic fiber came in use for fishing nets, the more interests have been paid for decreasing the deformation of net due to currents so as to enhance the fishing efficiency.
In continuation to the previous paper¹⁾, experiments have been carried out to clarify the different inclinations of nets constructed of various kinds of fibers, the materials of which are listed in Table 1. Using a net stretched to a frame with an area of one square meter to make the mesh square, one side of it was kept on the water level, and the vertical distance h was measured at a current speed v in a way shown in Fig. 1. Next, the inclination of the frame without the net was also determined in the same way.
Then, the inclination of the net alone was calculated by deduction this inclinate effect of the frame itself from the former one.
Thus, the relations between the inclination h and the current speed v were obtained as shown in Fig. 2 according to different materials of the nets.
From the calculation, the weight of the net per unit in water w, under water speed v and angle cf inclination θ, is expressed on the bases of diagrams in Fig. 3. by a formula:
w=a•d/l•tanθ•v²
where, d is the diameter of thread, l the size of a mesh and d the coefficient of resistance. It is noticed that the nets which are made of endless synthetic fibers such as Amilan (Polyamid), Saran (Vinylidene chloride), Kurehalon (Vinylidene chloride), Tevilon (Vinyle chloride) and Silklon (Polyvinyle alcohol) are larger in the value of a than the nets of natural cut-fibers. In other words, a is the coefficient chiefly depending upon roughness of the surface of the netting cord. In order to decrease the inclination of nets, it is desirable to make the value of w as large as possible.
a•(d/l)

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In discussion of the magnitudes of animal or fish populations the Verhulst logistic equation has usually been taken as a point of departure. In this expression, density-dependent causes of mortality could affect the abundance of either the existing adult stock and the young which it produces. But, on the contrary, W. E. R_ICKER treats subjects of populations and equilibrium level of exploitation from reproduction curve under the assumption that no compensatory mortality occurs among mature stock. Both in earlier treatments and in R_ICKER's, dynamic population parameters are implicit, though static characteristies are considered.
In this paper, the writer attempts to summarize the basic theoretical information expressed in the differential equation of population dynamics, recognizing in his formulation the formal distinction between stock and recruitment. It is concerned with predicting what change of stock or catch can be obtained from a given aspect of young fish recruited to a fishery. That is, changes cf abundance of stock, s, are related with recruitment, r, by the fundamental equations (1) and (2). Population parameters α, α_n and α are instantaneous mortality rates-total, natural and fishing respectively: c is total catch. Recruitment will not mean, the initial number of eggs or newborn young, but the number of young surviving to the specific age or the commercial size.
Refering analogously to other dynamic systems, recruitment is the intensive quantity like excitation potential, signal or input voltage and stock is the extensive quantity like response or output by the adequate transformation of corresponding variables. In an electrical system (Figs. 1 and 2, eqns. (3) and (4)), electric current, i, or output voltage e₀, corresponds to stock. Exciting or input voltage, e or e_i, corresponds to recruitment. Elements of circuit (inductance L, resistance R and capacity C) determine system parameter α or time constant T (reciprocal of α). In a mechanical system (Fig. 3 and eqn. 5), external force F, and displacement x, correspond to recruitment and stock respectively, α or T is determined by elasticity of recovering spring and damping resistance of dash pot. In a hydraulic surface system (Fig. 4 and eqn. (6)), head of hydraulic surface x and inflow v, stand for stock and recruitment respectively. Surface area and dimensions of outflow tube determine system parameters.
With application of these transformative relationships, an analogue computer could be built up in order to elucidate the mathematical problems of populations and to obtain graphically the variation of catch.
If r is impulsive, indicial and sinusoidally periodic, s is expressed in egns (7), (11) and (13), Fig. 5 and 6. Provided r is generally periodic and of random form, s is expressed in egns, (19), (10) and (23) by the principle of superposition.
In the present investigation attention has been directed toward a dynamic study of the explicit reiation between the magnitude of population and recruitment in the case of a single fish population. But fishing changes the absolute abundance of mature fish in a stocx, and may affect the numbers of recruits in subsequent years. Furthermore, it is important to consider the case of two or more coexisting populations. The writer will attempt to discuss these problems in later papers, regarding them as the feedback problems of networks of circuit systems.
The example given here deals with the fishery for anchovy larvae and young at Maisaka in.

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The boundary zone between different water masses in the open sea has been recognized by fishermen as a good fishing ground of various migratory fishes inhabiting in cold or warm waters. Many works have been done by many investigators on the physical aspects of the boundary zone and the ecology of individual fishes involved in it. The most of these works have been rather conformed with qualitative concepts which have been recognized for many years. For the standpoint of fisheries, however, more quantitative approaches will be required.
At the first step, we consider the plankton population in the boundary zone as an indispensable source of energy to support the metabolic activity of fishes. Under this assumption, the boundary zone should be the place where the active metabolic exchange of energy is taking place between fishes and their environments, and it must be more fertile in the food materials than other areas.
The present work attempts to evaluate the fertility of the boundary zone in precise terms of metabolic energy source by chemical methods. For this purpose, it is desirable to determine the, organic content of the plankton population by direct analyses of the samples collected with plankton nets. However, there are difficulties of dtvising a plankton net suitable enough to meet the demands of this work and at the same time simple enough to be usable for practical application. In addition, we have neither the information nor the available data for the development of such work.
Hence, the studies are developed for methods of estimating the approximate organic content of the plankton populations by the increase of the oxygen from a certain oxygen level in a given region. The outline of the estimation and the assumptions involved will be only briefly summarized here.
If all the waters from which the production of phytoplankton had been. originated were saturated with oxygen, and the oxygen exchange with the atmosphere during the period of the production had no significant effects upon the distribution of the oxygen, it might be expected that the oxygen supersaturation would be approximately equivalent to the amount of the oxygen liberated by photosyn. thesis of the plant. Under such conditions, the amount of organic material synthesized by the phytoplankton in a unit volume of water can be expressed as carbon corresponding to the oxygen increase, since for every molecule of carbon dioxide utilized by phytoplankton, one molecule of oxygen is liberated. In many cases, however, the organic carbon synthesized by phytoplankton is converted by grazing processes into that of the other forms of organisms such as zooplankton, fishes and other larger animals, and partly returned to carbon dioxide through metabolic processes or by disintegration of the organisms. On the other hand, the oxygen of waters should be reduced remaining the oxygen equivalent to the organic carbon of the plankton population. Hence, assuming that the respiratory quotient is 1, it is possible to estimate the carbon c?ntent of plankton population contained in a unit volume of waters by using the observed supersaturation of the waters.
However, it is considered that the oxygen supersaturated by the phytcplankton in the surface water may be partly driven off towards the atmosphere. On the other hand, it has been already known by many workers that in the euphotic layer, for each milligram of phosphorus utilized in photosynthesis, the phytoplankton will take up 76ml. of CO₂ and release the same volume of oxygen, and at lower levels, where regeneration is taking place, the consumption of 76ml.

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If there are the data on the distribution of temperature, salinity, dissolved oxygen and phos phate in a given region, it is possible to estimate the standing crop of plankton population from the oxygen supersaturation by using the method described in the preceding paper. Unfortunately, however, we have little such complete data on the oxygen distribution covering different seasons and places for the practical calculation of the standing crop in the sea area surrounding the Japan. Therefore, in this paper, a statistical method is developed for the evaluation of the oxygen supersaturation.
The method has been based on the relationship between the oxygen supersaturation and the water temperature, and their statistical treatments have been made by using the data described in a series of publications of the Central Meteorological Observatory and the Imperial Fisheries Experimental Station in Japan respectively on temperature, salinity and oxygen distributions in the eastern sea of Japan (see references). The frequency distribution of the oxygen supersaturation against the different grades of water temperature in the eastern sea of Japan is given in Table 1. The values of the oxygen supersaturation in each water temperature are averaged respectively and plotted into Fig. 1 in the range of water temperatures from 11°C to 25°C together with the actual determinations for micro-plankton organisms obtained by T. S_HIMOMURA, 1953. As shown in Fig. 1, the maximum oxygen supersaturation which should be corresponded to the maximum standing crop of the plankton is found in the range of temperature from 14°C to 17°C and fairly agrees with the actual maximum amounts of mieroplankton organisms. However, the actual determination shows the another mode of plankton population at the range of temperature from 8°C to 9°C. For the lower range of temperature than 11°C in this area, the available data on the oxygen distribution have been very scant, so that the data on the Japan Sea have been refered, even if they might be unadequate (Fig. 2). According to Fig. 2, the mode of the oxygen supersaturation is found at the range of temperature between 4°C and 9°C. Therefore, from these facts it is assumed that there would exist a fertile zone also in colder sea areas than 11°C.

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The experiments on the effects of the various kirds of organic fertilizers and those of addition of the chemical ones to them on the reproduction of Cyclops hyalinus were carried out. Each combination of these fertilizers and these effects to reproduction of this species are shown in Tables 1 & 2. In every case, the organic fertilizer to which the calcium superphosphate was added showed the best influence to the rate of reproduction of this species. From these results, it will be considered that the optimum value of the ratio N:P₂O₅ contained in the fertilizer to the rate of reproduction of Cyclops is tsmaller han that in case of Daphnia (2:1 ?? 3:1) already reported by the author³⁾.

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The experiments on the effect of the chemical fertilizers added before and after the administration of the organic ones to the rate of reproduction of Daphnia longispina was carried out. In case of using the fish meal as the organic fertilizer, no remarkable effect by the addition, of the chemical one was seen. But, in case of using the rice bran as the organic fertilizer, the effect of the chemical ore added at 3 rd day since the supply of water could be recognized and especially the ammonium sulphate as the chemical one produced the good reproduction of this species (Tables 2 & 3).
Moreover, Daphnia to which the rice bran, as the orga ?? ic fertilizer was given became red and this phenomenon was considered to be caused by their living food.

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Oxy-and met-hemoglobin crystals were obtained from the blood of several kinds of fish, i.e., Thunnus orientalis (immature), Katsuwonus vagans, Cyprinus carpio, and Seriola quinque-radiata, etc., by S_CHULZ's method, by D_RABKIN's method or by the modification of the latter (Fig. 1), and studied spectrophotometrically.
The spectra of various derivatives of these hemoglobins were then compared with those of horse hemoglobin prepared for reference (Fig. 2, Table 1), and it was found that there are neither so marked specific differences between fish and horse hemoglobins, nor between fish hemoglobin as seen increases of myoglobins of fish and higher vertebrates.

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Previous paper¹⁾ from this laboratory has reported the amino contents of the ordinary and the red muscle proteins of some fishes. Microbiological technique employed in the previous work was extended further to 10 species of common fish, which are important and representative species for Japanese foodstuff, and content of 17 amino acids of the ordinary muscle proteins prepared from these fishes were determined. The results obtained are tabulated in Tables 1-3.
It was expressed in the previous report that amino acid composition of the fish muscle proteins analysed were relatively uniform. The same result was obtained in this study, too, although some slight differences were observed in several amino acids, especially in aspartic acid.
Therefore, it may be possible to state that the amino acid composition of the fish muscle protein is relatively constant without distinction of species, including the cuttlefish and shark.
Furthermore, it is noteworthy on the nutritional point of view that the content of essential amino acids of the cuttle-fish muscle protein are almost same as those of the fish.

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An outbreak of allergy-like food poisoning occurred in Kawasaki, Kanagawa Prefecture, on August 19, 1954, in which all of 11 persons who had taken cooked frigate-mackerel meat fell ill. Another outbreak of similar food poisoning was observed on October 16, 1954, in a factory at Hamamatsu, Shizuoka Prefecture, in which 90 developed allergy-like symptoms among 400 persons who had consumed “samma sakuraboshi” in their lunch.
In both outbreaks, similar symptoms of characteristic as ob ?? erved in the cases previously occurred in 1953 were recorded.
Chemical anaylyres of the incriminated materials of both outbreaks as well as ordinary market material showed no significant difference in the contents of volatile basic-N or trimethylamine-N between them. However, much amount of histamine and of total vagusstimulant were observed in. the crude methanolic extracts of the causative food. The latter was estimated by Magnus' method using intestine of guinea pigs.
The toxic substance other than histamine was successfully isolated and was identified as “saurine”, which is an autonomic nervous toxin like histamine recently isolated by us. The high content and the wide distribution of histamine and “saurine” in each material of incriminated foodstuffs may suggest that these poisons should be the main causative agents in allergy-like food poisoning.
As for the extraction of these toxic substances, histamine was easily extracted according to such ordinary process that with methanol → absolute ethanol → methanol. On the other hand, “saurine” could hardly be extracted by above procedure. Very slight solubility in absolute alcohol of this substance is the one of the marked differences from histamine.

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The effect of trimethylamine (TMA) or trimethylamine oxide (TMAO) added to histamine, or “saurine” (an autonomic nervous poison like histamine recently isolated by the authors) was examined according to the contraction method (Magnus') using intestine or uterus of guinea pigs. Results obtained are as follows:
1. Using uterus, sometimes synergistic action of added TMA or TMAO to either histamine or “saurine” was observed to a certain extent, and sometimes no action was recorded in the same experiment. These irregular results might have been due mainly to the nature of contraction of uterus. However, even when positive synergism observed, the rate of increase in the action of his tamine or “saurine” was less than 10%.
2. In no case, synergistic action was observed in the experiment using intestine. Results obtained are summarized as follows.
Concn. of histamine or “saurine” Range of concentration of test solution in M at which no synergistic action occurred
histamine 2γ TMA 0.5×10^-3-0.5×10^-8M
?? 2γ TMAO 0.1×10^-5-0.5×10-8M
?? 2γ histidine 1×10^-4-1×10^-7M
“saurine”
0.3cc (1.5γ equivalent histamine) TMA 0.9×10^-2-0.9×10^-7M
0.4cc (2γ ?? )TMAO 0.9×10^-2-0.9×10^-7M
0.2cc (1γ ?? ) histidine 0.9×10^-3-0.9×10^-7M
3. From the results above described, both TMA and TMAO could not be considered to have any synergistic action upon histamine or “saurine”.

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As shown in our previous paper, V, neither trimethylamine (TMA) nor trimethylamine oxide (TMAO) was described to have any recognizable synergism on the action of histamine or “saurine” to contract intestine or uterus of guinea pigs. This paper also deals with the effect of those substances when added to histamine or “saurine” tested by shock symptoms in guinea pigs, skin reaction in rabbits and lethal dose for mice (LD₅₀).
The addition of TMA or TMAO resulted in no appreciable change in the action of histamine of “saurine” Per se in each experiment. Therefore, the presence of TMA or TMAO, if any, coald not be regarded to stand as a cooperative factor to either histamine or “saurine” in a foodstuff responsible for allergylike food poisoning.

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Preceeding report¹⁾ showed that addition of the boiled extract of several shell-fishes at about 3% level resulted in a noticeable chick growth response. Since it can be presumed that the response may be most probably due to the APF which was extracted from the viscera, a study has been made to see the effectiveness of an autolyzed viscera to chick growth and further to fractionate the growth-promoting principles. The results can be summarized as follows.
1. Supplementation of an autolyzed viscera at a 1.7 per cent dry basis level gave a remarkable growth response of chicks fed a basal ration of all-vegetable protein.
2. Addition to 100g basal ration of 0.27g of the activated charcoal adsorbate which is equivalent to 2.8g of the dried autolyzate, resulted in growth promotion of one-month old chicks during six-week feeding as contrasted to a negative result on addition of 1.35g of the non-adsorbed fraction.
3. It has been found that the adsorbed fraction promoted both body growth and the development of the gonad, whereas the non-adsobate apparently promoted only the latter.

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