The present paper embodies my observations on the rates and the velo-cities of the bacterial decomposition of the extractive matter of the meat of several kinds of aquatic animals, and on the growth rate of bacteria in the solution of the extractive matter.

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(1) Age of bonito was determined on the basis of the vertebral bones just like that of chub-mackerel. The body length (l) of bonito well correlates with the length (T) of the cent-rum of the vertebral bone (Fig. 1). The rings (r) formed on the surface of the centrum can be considered as the year rings. The first ring measures 2•5mm in radius, the second one 3•9mm, the third one 5•4mm, and the fourth one 7•2mm. When the body length is 26cm, the length of the centrum (T) becomes equal to the radius of the first ring (r₁) and thus the ring may be completed. Therefore, the bonito less than 26cm in body length may belong to 0-year group. According to the similar assumption, I-year group ranges in body length from 27cm to 34cm, II-year group from 35cm to 43cm, and III-year group from 44cm to 53cm. IV-year group may be larger than 54cm. (2) Most of the bonito caught by angling are mainly com-posed of III-and IV-year groups in the Liu-Kiu region, and III-year group occupies 60% of all and IV-year group 40%. While bonito shoal is simply composed of III-year group in the Tô-hoku region. It is also remembered that bonito caught by long lines is far larger in size than that by angling and usually belongs to V-year group or far older one. (3) There are two differ-ent shoals of bonito in these regions. The one is the migratory shoal and the other the resi-dent shoal. The resident shoal is gener ?? lly larger in the mean value and in the modal value of body length than the migratory group either in III-year group or in IV-year group. The migratory group is simply composed of III-year group in the Tôhoku region, while the resident group comprises to some extent IV-year group. The migratory group is higher than 20 in the quality-indicator (10₃. W/L₃), while the resident group less than 20. In the Liu-Kiu region, the resident group is fished principally in the area around the small isles and over the shallow banks. The resident group is also related with small isles of the Bonin Chain, although it can migrate north-eastwards into the open sea of the Tôhoku region. On the other hand, the mi-gratotry groups are fished in any portion in both regions. (4) The migratory shoal of III-year proup in the Tôhoku region is probably originated from the migratory shoal of III-year group in the Liu-Kiu region, because shoal of similar character to those in both regions can be fished in the Seinan region. The migratory shoal of III-year group can be called the Liu-Kiu group both in Seinan and Tôhoku regions. While, the resident groups in both regions show no simi-larity in any respect to each other. In addition, no resident shoal is fished in the Seinan region between these two regions. According to the distribution of the fishing positions, the resident shoal seems to migrate into the Tôhoku regions from the southern sea through the Bonin Chain. Therefore the resident shoal can be considered as the Bonin group in the Tôhoku region. The migratory shoal occupies 60% of total catch and the resident shoal 40% in the Liu-Kiu region. In the Tôhoku region, the Liu-Kiu group occupies 80) of total catch and the Bonin group only 20%. (5) The fluctuation in the yield of these regions seems to be influenced by the changesin the age composition in the Liu-Kiu region, and also in the. ratio of the resident group (the Bonin group in the Tóhoku region) to the migratory group (the Liu-Kiu group in the Tôhoku region).

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The influences of the drainage from a rayon-factory and of urbiflcation of the bordering districts on the fisheries in Lake Biwako are studied from the statistics of the catch and of the number of fishermen, collected according to towns and villages.

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In the present study, the materials of which are based on the records, for April of several years, of the large hauls of spring herring on the Japan Sea coast of Hokkaidô as well as on the weather charts of the Central Meteorological Observatory, the conditions of wind, either avourable for the large hauls or not, are examined.

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In order to study and to improve the manufacturing process of the fish-hook, for which old proprietary experience has hitherto been consulted, we have carried out some experiments in the Physical Laboratory of the Imperial Fisheries Institute under the guidance of Dr. M. T_AUTI.
By means of a specially designed electric furnace, various thermal treatments were applied on about 3, 000 raw materials of similarly shaped bonito-book of 3, 4•5 or 5•4cm. in length, the heating temperature θ₁ and the duration t₁ having been changed in the range of 730° ?? -900°C and of 60 to 226 minutes respectively, while those of the annealing θ₂ and t₂, in the range of 200°-400°C and of 2-27 minutes respectively. Then, the breaking load, W, and the deforma-tion of the book were measured by means of Mori's tensionmeter also specially devised.
The results are summarised as follows: -
(1) In the range of θ₁ of 780°-820°C and of θ2 of 250°-300°C, both of which are compara-tively high for 3cm. -hook and low for 4•5cm. or 5•4cm. -hook, a maximam breaking load, W_max., was obtained.
(2) The most favourable points of t₁ and t₂ are 60 minutes and 2-4 minutes for 3cm. -hook, 160 minutes and 3-6 minutes for 4•5cm. -hook and 226 minutes and 4-8 minutes for 5•4cm. -hook, respectively.
(3) Under various thermal conditions adjusted according to the law of similitude, in general, W varies as the second to fifth power of the size of the hook, d, but, for θ2, as high as 350°C and t₂ above 10 minutes, we see that W is proportional to d² approximately.
(4) Taking into consideration the degree of deformation of the samples, the change of a quantitative measure of the plasticity η owing to the increase of θ₂ and t₂ is as shown in Table 3.
(5) If we combine the results (1) and (2), we may be able to find a more excellent manu-facturing process of the hook than before.

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The smallest post-larva of the present species which the author could obtain is 5mm in total length. This early post-larva represents the so-called “white fish” stage, a form charac-teristic to the clupeoid post-larva with transparent, elongated body. There are about 51 myo-tomes in the body, and the anus lies under the 45th myotome. The characteristic arrangement of the black pigments along the upper and lower sides (sometimes only on the upper side) of the body near the tip of the notochord, and the far backward situation of the anus are the characteristics by which the early post-larva of the present species is distinguished from those of the related species found in Korean district. The early post-larvae of about 5-9mm in total length were captured by surface tow in May to July, in the eastern part of the Korean Strait and along the south and west coasts of Korean Peninsula. During growth, the anus and the dorsal fin of this “white fish” shift forward, but the ventral fin scarcely changes its initial situation. The body gradually increases in height and becomes compressed. At a length of about 35mm, the surface of the body becomes wholly scaled, the relative position of the fin and the anus settled, and the post-larval “white fish” stage is passe ?? over. Then after-wards, a black spot appears in the shoulder region, the hinder-most ray of the dorsal fin Legins to stretch out, and the snout covers the lower jaw, and the general appeara ?? ce of the body approaches that of the adult form.

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After having verified that there was no difference in the chemical constitutions among the fishmeals which were sifted out so as to consist of granules of different sizes (I, II, III, IV), the author measured, by the same method as used in the previous report⁽¹⁾, the diffusivity constant, K, of the moisture in the pile of the meal and the total moisture absorbed, Q in a definite time, t. From the results (Tab. 2, Tab. 3) we can see that the smaller the size of fishmeal, the greater become both the constant, K, and the moisture, Q.

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The fish can digest food in winter, even though the temperature of its body is nearly as low as that of the environment during that season. It may be expected, therefore, that the digestive ferments of the fish are more active at lower temperatures than is the case with those of warm-blooded animals. But the literature is not consistent on this point. The optimum temperature for the proteolytic ferments of several kinds of fishes has been reported to be above 40°C by various authors, such as LUCHAN, RICHET and MOURRUT, OSHIMA and SASAKI, MACHIDA, YA and SHIMADA, OYA and HATANAKA, OYA and YOKOTA, OYA, KAWAKAMI and SUZUKI, TAKAHASHI and HIROSAWA. On the other hand, certain temperatures below 40°C have been shown to be the best for the activity of the proteolytic ferments of some fishes by FICK and MURISIER, HOPPE-SEYLER, RAKOCZY, SHIMADA and NITO. The question naturally arises as to whether or not such direrepancy is due to degree of lowness of the temperature of the water, in which the examined fishes live. Casting about for fish which lives in colder water, On ?? orhynchus adonis J_ORDAN, which lives in Lake Towada (the temperature of its water is below 25°C, even in summer), was chosen. The glycerine-extracts of stomach, intestine and pyloric ?? oe ?? a were prepared, and the optimum temperature for the proteolytic ferments was found to be ca. 30°C.
From table 2, it is seen that the optimum temperatures of the proteolytic ferments of the various fishes vary with the temperature of water, to which the respective fishes are ac-customed.

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The flat surface of fine alminum powder covering the upper end of a can up to the height of seaming edge except the central part, at which the can is beaten repeatedly, gradually ex-hibits a vibration figure as shown in Fig 1. Employing 1/2 lb salmmon cans, the author pho-tographed their vibration figure, divided the cans into six groups according as its pattern and knew that there are close relations of it to the weight, W, and vacuity V, of each can.

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