Standing crops of phytoplankton were measured by using some different methods in three large fire pools (40m^2,2.5m in depth) in Tokyo from 1951 to 1953. (1) The amount of seston increased in the spring and the autumn (20mg/l), and decreased in February and March (5mg/l). It was larger in the bottom layer (2m layer) than in the surface layer. The amount in Pool A was 1/3〜1/2 of those of other pools. Ignition loss amounted to 50〜90 per cent, and was largest in Pool A. It was generally small in winter. It was large in the surface layer in the summer and in the lowest layer in the winter. The seasonal changes and the vertical distribution of the organic matter in seston were about the same to those of seston. It showed nearly the same value in each pool(15mg/l in maximum, 1mg/l in minimum), which were somewhat larger than those of the common eutrophic lakes. (2) The amount of evaporation residue was 120〜150mg/l in average in each pool. It was large in the bottom layer. Maximum values were seen in the spring and the autumn. The ignition loss was 20〜70 per cent. The amount of organic matter was about ten times as much in the evaporation residue as in the seston. The maximum value of the former is seen a month later than that of the latter. (3) Nearly the same tendency was seen between the seasonal changes in the amount of the consumption of KMnO_4 and of the organic matter in the evaporation residue, or between the amount of albuminoid-N and of the organic matter in seston. Amount of the KMnO_4 consumption was 10〜40mg/l, and of albuminoid-N was 0.3〜1.0mg/l. These contents in Pool A were a little less than in Pools B and C. (4) In the chlorophyll content of waters, two maxima were seen in the spring and in the autumn, and two minima in the winter and in the midsummer in each pool. The content was large in the lower layers in Pool A, and in the upper and middle layers in Pools B and C. It ranged from 3 to 80mg/m^3,showing the same degree of the content in eutrophic lakes. Three years' data showed that the monthly mean amount in Pool A was 1/2 of Pool B, and Pool C was 2/3 of Pool B. The amount of phytoplankton calculated from the amount of chlorophyll was 0.1〜3.0mg/l, being 5〜20 per cent of the organic matter in seston. (5) TThe above facts showed that a large amount of detritus and heterotrophic plants were involved in addition to green plants in the seston of these fire pools. For this reason it is difficult to estimate the amount of phytoplankton from the amount of organic matters in seston. It is especially marked during the turn-over period.Consequently, it can better be computed from the chlorophyll content. For the more precise computations the correction according to the qualitative nature of the plankton is needed. It is especially important. when diatom is abundant.
In the first report of this series of study (OTA and TAKATSU 1956), we described the changing process of habitat segregation of three species of the Muridae, Clethrionomys rufocanus, C. rutilus mikado and Rattus norvegicus in a small tree stand, and we discussed mechanism of habitat segregation. In that paper we emphasized the interaction of populations rather than the habitat selection as the main cause of habitat segregation. But the conclusion of the first report was found to be partly in need of reconsideration. I shall describe some aspects of the habitat segregation of the three species of murids in the first year of the study, and correct and supplement the conclusion of the previous paper. In the small tree stand described previously, C. rufocanus, C. rutilus and R. norvegicus live together and separately. The former two are related closely, but the latter is not only a distant ally of the formers but sometime a facultative predator of them. In spring, when each population density was low, each lived separately in the survey area. Toward summer, as each population grew large, the distributions of the three species were overlapped, but each had its own denser populated area. Although the occurrence of each species was not strictly associated with the conditions of the area, generally speaking, C. rufocanus occupied the open-dry part, C. rutilus the shaded-wet part and R. norvegicus the sides of the river and the drainage. As described in the first paper, a field experiment was done in summer to determine the cause of the habitat segregation. The populations of the two species of Clethrionomys were transplanted to the area from the other place after removing the former inhabitants. The two immigrant populations settled in the area separately. Similar to the former inhabitants, C. rufocanus occupied the open-dry part and C. rutilus occupied the shaded-wet part of the area, further both exploited the vacant site which was formerly occupied by R. norvegicus. R. norvegicus was not transplanted, but many new individuals of it appeared on the outside of the drainage around the area, and very few of them appeared on the inside of the drainage. Thus, the habitat segregation became clearer in this time than in spring. From the result of this experiment, it should be concluded that the habitat segregation of the two species of Clethrionomys is due to habitat selection and the habitat segregation between R. norvegicus and Clethrionomys is due to interaction (competition). But at the same time, interaction was also found between the two species of Clethrionomys because some replacements and interminglings of individuals were seen between their occupations of habitat, and the habitat selection of R. norvegicus was also found because the rats always occurred along the river and the drainages. Toward autumn, the populations of two species of Clethrionomys declined and they showed no segregation in the area, while the population of R. norvegicus grew large on the outside of the area and a few rats went into the inside. The rats were foraging crops of the field around the area. This type of segregation between R. norvegicus and Clethrionomys is certainly due to habitat selection. Habitat selection and interaction are two aspects of habitat segregation and they act in combination, and which of them acts mainly is determined by the intrinsic and extrinsic conditions of the species. Furthermore, in the lives of higher animals, psychological factors may be effective to habitat selection and interaction. Two different cases of co-existence were observed in this area. The one was found in the time of population growths of the three species and the other was found in the time of population declines of the two species of Clethrionomys. The former case is commoner than the latter and it is usually interpreted as a process of competition. The latter case cannot be considered as competition, and it is postulated as a process of disolution of inters
This experiment was made with 39 leading varieties of sesame seeds collected from seven countries including Japan to the change in germination conditions due to the passage of storage years since 1952 to 1957. The difference was seen among the varieties, and the relation to their several characters (seeds from Israel produced in 1952 were not used). The seeds were stored in the seed containers at room temperature. During the experiment a Jacobsen germinater was used for making the germination rate : 3 days, germination ratio : 10 days at 35℃. This experiment was made in 1957 and the results obtained are as follows. 1) Germination markedly dropped after the storage of five years, the worse case being that of the African varieties (germination ratio : about 10%) and the best that of the Japanese or Chinese varieties (germination ratio : about 30〜40%). 2) Those of the American varieties showed 50 per cent germination ratio after the storage of three years. Those of the Indian, Israel, Japanese and American varieties needed four years to gain the same result. 3) When the sesame seeds were stored comparatively carefully, their utilization period was four years and their longevity was five to six years. 4) Those of the temperate zone showed longer storage endurance than those of the tropical zone. 5) It took three to six days for the fresh seeds and seven to eight days for the old ones to germinate. 6) In the case of the fresh seeds the variety that contained more oil generally took more days to germinate. 7) When the weight of the 1000 seeds and germination coefficient of those harvested in 1953 were taken into covariance, in the case of the Japanese varieties : the lighter the seeds, the higher germination coefficient followed. In the case of the American varieties : some showed just the same phenomena as the Japanese varieties and some just the reverse. As for the seeds harvested in 1957,in the case of the African origin : the germination coefficient was higher when some seeds were heavier and when others were lighter. 8) When oil contents and germination coefficlent of those harvested in 1953 were taken into covariance, in the case of the American varieties : the more oil they contained, the higher germination coefficient they showed, while those of the Indonesian varieties, the less oil they showed. When compared with those harvested in 1957,in the case of the Japanese varieties, the more oil they contained the higher germination coefficient was obtained.
The containers made of bamboos aged two months (I), three months (II), one year (III) and three years (IV) were set in the field, and the biotic community in each of them was investigated ecologically with special reference to the succession of the Protozoa. 1. The appearance of Diptera larvae was characteristic in I-IV and closely related to the occurrence of the Protozoa association. 2. The water situations were similar to each other in the fauna of Protozoa and differed in the velocities of their succession ; namely, in I, it changed rapidly, in II, following I, and in IV, changed most slowly. 3. The characteristics of the velocity of succession was explained by taking the progressive changes of the amount of matter into consideration. 4. When the bottles containing the bamboo juices with different concentration were placed in the field, they were characterized by a definite seral stage of the protozoan succession after bacterial contamination.
The azuki bean weevil which had been reared continuously under constant laboratory conditions for many years using the azuki bean, Phaseolus angularis Wight, for food, was removed to the soy bean, Glycine Max Merrill, The growth form of the weevil population was investigated in the soy beans by counting the adult weevil every week. It was found that the growth of the third generation was greater than that of normal cases (Fig. 1). The reason was analysed experimentally. The results of experiments were analysed concerning with the change of sex ratio, developmental period, mortality, and fecundity with successive generations. The sex ratio and the developmental period did not vary regularly with the progress of generation (Figs. 2,3), but the fecundity increased remarkably (Fig. 4) and the mortality decreased slowly with the advance of generation (Fig. 5). Therefore the rate of increase as represented by the number of progenies per female increased with generations (Fig. 6). It became clear that the reason why the population growth form of the azuki bean weevil removed from azuki beans to soy beans did not show a normal form was partially the increase of reproductivity with generations. In discussion, it was considered that the selection was insufficient to interpret these results.
When the spore of Equisetum is soaked in water and kept at temperature of about 20°to 25℃, it begins to germinate in several hours. The spores of Equisetum arvcnse L. were soaked in 10ml of tap water filtrated through the exchange resin. The first investigation was carried out to determine the relation between the density and the germination of spore. The quantities of spore, which were soaked in 10ml of water, were 10^<-1>, 5×10^<-2>, 10^<-2>, 10^<-3>, 10^<-4>, 10^<-5>and 10^<-6>g. The spores in water sank to the bottom. Therefore, the bottom area of container influences the germination of the spores soaked in water. The optimum density of the spore was from about 4×10^<-3> to 1×10^<-4> g per 10sq. cm. The higher density of spore inhibited remarkably the germination in water, but there was no great difference in the rate of germination among a series of the lower densities. This optimum density(4×10^<-3>g per 10sq. cm)was equivalent to 10g of spore per 10ml of water in the Petri dish with about 5.5cm in diameter. All the following tests were carried out in the optimum density using the Petri dish. The spores did not germinate in 8 hours after soaking in water at about 23℃, but germinate by 24 hours. They did not germinate in water of 5℃. The study on the effect of water-exchange on the germination of spores in water was performed as follows : (1) The water in which the spores were soaked at about 23℃ was exchanged for fresh tap water after 8 hours from the beginning of the experiment. The spores were exposed to scattered light during presoaking process. (2) The water in which the spores were soaked at 5℃ was exchanged for fresh tap water after 24 hours. The spores were placed in the dark. (3)The water in which the spores were soaked at 23℃ was exchanged for fresh tap water after 24 hours. The spores were exposed to scattered light for the first about 10 hours of presoaking process. In (1) and (2), when water was exchanged, the spores did not germinate yet, but in (3) germinated already. After exchange of water, all the sets were placed in the room of about 23℃, and the spores were observed on the germination after 30 hours. The sets in which water was exchanged before the germination of spores showed a decrease in the rate of germination as compared with that of the respective controls in which the water was not exchanged. Exchanging water after germination gave no effect on the subsequent growth of rhizoid.