The present investigation was undertaken to modify the oil-water flotation method for the purpose of a more effective extraction of larvae and pupae of aquatic midges from a soil sample. First, a sample of soil was stirred by a magnetic stirrer for more than three minutes in a beaker containing CaCl_2 solution having a certain specific gravity to remove the insects from the soil tubes and to float them to the water surface. Secondly, the floating insects were separated from other floating materials by use of benzene and air evacuation. In this process the specific gravity of a solution should be determined in correspondence with the total time required for the treatment. Also the pupae which could be scarcely wetted by benzene should be pushed up to the benzene layer by large buoyancy in a solution having a specific gravity above 1.30. Lastly, the insects were locked in the benzene plug upon freezing of benzene and examined after the benzene plug was thawed.
Continued from the previous report, this one deals with the percentage of works shared between the male and female, territory, predator, family life and reproductive rate, based on the results of outdoor observations for the purpose of studying the life history of the birds in the Zenkoji basin (altitude about 400m) in the northern part of Nagano Prefecture from 1963 to 1964. The main part of the observations was done in the Nagano district in the center of the basin, and most of the life history during the breeding season of the bird was described based upon the observation of one nest in 1964.
1. The present studies were undertaken primarily to describe and classify the Pinus pumila scrubs of Hokkaido in Japan on the basis of methodology of the Zurich-Montpellier school in phytosociology. 2. The investigations were carried out in the Daisetsu and the Hidaka ranges located in the central and southern parts of Hokkaido respectively. The homogenous parts of vegetation were analyzed by recording the dominance and sociability of all species including cryptogamic as well as vascular plants in the sample plot of 5×5m which well exceeds the minimal area needed. 3. The vegetations investigated were classified according to fidelity of species and species combination. The vegetation units employed in the studies are alliance, association, and subassociation. 4. The following three associations and seven subassociations were established in the studies, namely, Assoc. Sorbeto-Pinetum pumilae : Subassoc. spiraetosum aemilianae and leucothoetosum yezoensis ; Assoc. Rubeto-Pinetum pumilae : Subassoc. typicum, sorbetosum matsumuranae and ledetosum diversipilosi ; Assoc. Ledeto-Pinetum pumilae : Subassoc. typicum, and dicranetosum scoparii. Each of the associations classified was described in the table showing the floristic composition and the data of growing habitats. 5. The interrelations of the subassociations classified were examined on the basis of index of similarity.
It is suggested that the small individuals of the under-yearling fish population, less than about 6cm in body length may drop from the population during winter and these fish are inferior to the large ones in condition factor (MAKI, 1966b). NIKOL'SKY (1963) points out whether the fish succeed in "over-wintering"depends largely on how much they deposit fat in their body during the growing season. The relation between the"over-wintering"of the under-yearling fish and the fat content in their body is reported in this paper. The sample specimens of the adult and sub-adult were taken from commercial landings between August 1965 and May 1966. The specimens of young fish, less than about 4cm in body length were collected by the author with a small trawl net in July 1966. Chloro-form-methanol solution was used for the fat extraction from the fish. The mean value of the fat content in the muscular tissue per unit of gram of body weight (wet weight) attains 16.6mg in late summer, which is the maximum of the year. Although this value tends to be maintained until March, a marked decreasing of the fat content in this part occurs between March and May, when the fish are maturating and then migrating to spawning beds. In May, the mean value of the fat content of this part decreases to 8.1mg, which is the minimum of the year. The mean value of the fat content around the internal organ also attains the maximum in late summer, 28.5mg per unit of gram of body weight and decreases to 20.2mg during the wintering migration periods. A significant reduction of the value occurs throughout winter and spring months when the fish experience wintering, maturation and spawning migration in sequence. The mean value of the fat content around the internal organ in May is 3.3mg, the minimum of the year. It is observed that the larger the fish grow, the more the fat deposits in their body exponentially. The fat content both in muscular tissue and around the internal organ increases accelerately when the fish size exceeds about 4cm in body length. The mean value of the fat content of small fish, smaller than 6cm in body length decreases more rapidly than that of large ones, larger than 6cm in body length, between December and May. This result suggests that the small individuals consume more fat in the body for energy source than larger ones during the over-wintering and maturation periods. In May, the spawning periods of the fish, the small individuals are scarcely found in the population. These facts may indicate that the small fish of under-yearling population are more disadvantageous than the large ones for over-wintering and maturation and drop from the population.
Regular surveys were made in 1965-1966 of the guppy population, which had been acclimatized in a short stream of polluted hot spring water in Togura-Kamiyamada spa (N 36°29', E 138°05') about ten years ago. Water temperature of the habitat was maintained at about 20℃ even in winter. These guppies were not cold-resistant. They showed so rapid growth and so great fecundity that they could attain an extreme high level in number (more than 2000/m^2). In summer they began to disperse to irrigation streams and rice fields, and the population number of the guppies in the short stream remarkably decreased. The guppies were euryphageous and they ate even attached bacteria and deposits of the stream. Four characters of tail figure were observed in the male fish. No tendency of shortening in tail length of the male in the natural conditions was observed.
A study was made of morphology, taxonomy, ecology, reproduction, and distribution in freshwater planarians of the species Phagocata kawakatsui OKUGAWA. The specific character in the present form of the copulatory apparatus is as follows : penis large with well-developed bulb and slender, long, finger-shaped papilla ; sperm ducts enter the penis bulb separately ; single bulbar cavity ; copulatory bursa rather small or moderate or large ; slender bursa stalk with thick radial musculature on the vagina. This species is distributed in Middle Japan (Honshu and Shikoku). Specimens from different localities show some variation in miaute details of the copulatory apparatus. This species in found in shallow spring-fed streams with a slow current. The planarians become sexually mature in winter to early spring (about six months after hatching). Their active breeding season is spring (March to May). After breeding, adult worms begin to die. One worm lays 1 to 2 ovoid-shaped cocoons in one breeding season. The number of juveniles per cocoon ranges from 2 to 10. An analysis was made of the factors affecting the seasonal change of the population size of Phagocata kawakatsui, and the taxonomic relation and speciation of the three Phagocata species (kawakatsui, teshirogii and iwamai) were also discussed.