1. The Shiia community of the central part of Sanyo district was investigated in 22 stands to observe the developmental stages of the community and the resultant changes in its composition and structure. 2. The ratio (in percentage) of the number of large diameter trees of Shiia spp. to the total of the same species was taken as an indicator of the developmental degree of the Shiia community. All the stands, excepting two on N-slope, were arranged in a gradual increasing order of the ratio, and these were divided into five groups by uniform interval (viz. interval is 20%). The series of stand groups thus obtained seems to show a developmental series of the Shiia community (Table 1). 3. In the series of the stand groups mentioned above, Shiia spp. shows the following trends : (a) gradual increase-maximum-gradual decrease in relative dominances and in total basal area, (b) gradual increase in mean area and average d.b.h., and (c) gradual decrease in density (Table 2 and Fig.2). These trends are nearly in agreement with the theoretical changes of these characters observed in the developmental series of the communities. 4. As for the relations between the developmental stages and the dominant species of the forest floor, it is found that Dicranopteris glauca or Bladhia japonica is a dominant species in undeveloped stands, while Dryopteris erythrosora is dominant in developed stands (Fig.3). Hence the Dryopteris erythrosora-floor type is taken as an indicator of the developed Shiia community in this region. 5. As regards the life-form spectra of Shiia community, the phanerophytes show, on the whole, the greatest percentage, and the hemicryptophytes, chamaephytes and epiphytes show lower percentages while the geophytes and therophytes are not found in any stand. Along the developmental progress from undeveloped to developed stands, the changes in spectra are relatively small, but in the case of hemicryptophytes, a gradual increase is observed (Table 3).
Three nests of Camponotus herculeanus japonicus MAYR were separately dug open and all the individuals of each nest were collected and measured as to the width of the head. The crude data obtained were as shown in Table 2 and the relative frequency distribution curves in Fig.1. All the individuals of one of the nests (Nest No.2) were measured in relation to the width and length of the head and pronotum, with the results of coefficient of correlation between them as given in Table 1. Judging by the range of their size distribution, the ants of this species have a potential ability to illustrate Curve A of Figure 2 under full-fed condition. When suppressed by an environmental pressure (in this case scarcity of food), it might change either into Curve B or into Curve C of the same Figure. That the actual curve obtained with this species of ants is neither of such curves, but Curve D, is resulted, according to the authors' opinion, from the regulative action of the worker ants against the environmental pressure (insufficient amount of food) which, maintains, on the one hand, the necessary number of individuals of the population at the sacrifice of the large individuals and, on the other hand, secures a small number of large individuals at the cost of the numerical dominancy of the population. However, the authors consider that the large individuals are brought about by mistake at the time when the ants breed the reproductive caste. According to the data obtained with Nest No.2,the ratio of the width to the length of the head is less than 1 in the small members of the population, 1 or nearly so in the medium-sized individuals and more than 1 in the large individuals (Fig.3). The result seems to give a suggestive evidence toward to opinion long believed among the myrmecologists that the dimorphism in the worker caste evolved from the polymorphic state through the extinction of the intermediate classes.
Suppose that there is a school of fish or shell of size N in a closed region A and a gear C is set in it at time t=0,then a region B will be formed around C. At first, individuals near the gear will be caught, individuals rete from the gear will approach to the gear and a part of them will be caught. After sufficient time elapses all individuals in a region A will be caught. Let the numbers of individuals in each state A, B, and C be u, v, and w at time t, then we have simultaneous differential equations (1)-(3) with solutions (5)-(7). An experiment was attempted in Kominato Bay by Babylonia japonica (REEVE) to ascertain the theory. The agreement between the experimental result and theory was good as is shown in Table 1 and Figure 2.
One of the special forest communities represented by Abies sachalinensis-Sasamorpha purpurascans var.borealis is developed at Ochiishi near Nemuro in Hokkaido. In the present paper, the compositions of this community were analysed by four belt-transects. Sasamorpha is generally distributed along the Pacific coast and a very few localities have been known along the Okhotak coast in Hokkaido. The easternmost distribution area of Sasamorpha was also studied accompanying with two quadrates (1m)^2.
The authors devised a simple new technic for studying the habit of Oncomelania, as follows. Oncomelania is put on the bottom of a Petri dish of ca. 10cm diameter and soon it attaches on the surface with its foot and begins to creep. Then the dish is put upside down under the dissecting microscope. So with the aid of the microscope the form and movement of its buccal mass is clearly observed and as a result of this its feeding aspect can be precisely persued. Applying such a technic we observed the feeding habit of Oncomelania hupensis and the result is as follows. 1. Among the artificial foodstuffs Oncomelania hupensis took the rice powder most rapidly, then wheat powder and lotus seed powder. 2. The mud from the habitat of Oncomelania is taken very rapidly by the latter ; at the same time the former is discharged frequently by the latter. Such facts suggest that Oncomelania usually feeds itself with the mud in its natural habitat. On the other hand a large quantity of diatoms (Naviculaceae) are found in its old feces as well as in the mud of its habitat, whereas they are rarely found in its feces immediatly after excretion. Such facts, suggest that Oncomelania in its habit at utilize those diatoms as its nutriments. 3. When Oncomelania was fed with calcium arsenate mixed with mud in various percentage, it took the mixture more rapidly as the percentage of calcium arsenate diminished. This fact indicates some facilities in case of applying this drug as a molluscacide.
A dense population of a salmon-like fish, Plecoglossus altivelis, or Ayu in Japanese, is found in the River Ukawa in the north-western part of Kyoto Prefecture. We have been studying the ecology of this fish from various viewpoints since 1955. This report concerns the change of the modes of utilizing the river-pools, which we observed during the course of our study. As we have already reported (KAWANABE, MIYADI, MORI, HARADA and OHGUSHI, 1956), there can be distinguished two kinds in the life of Ayu in pools, which are related to the topographical characteristics of the river-pools as well as to their adjoining riffles, i.e., using the pools as both feeding and resting places or as shelters only. By our recent observation it was discovered that the modes practically taken by Ayu might be changed according to population density. The population of Ayu by our estimation in 1956 was far less than that of 1955 (about one-sixth). The decrease in population in 1956 was far greater in the river-pools (about one-tenth of 1955) than in the riffles (about one-fourth of 1955). In 1956,when the density of Ayu in the river was low, the pools were utilized chiefly as shefters or resting places in the night-time, and the fish used to take their foods in the daytime in the adjoining riffles, where they could find better and richer food materials in the form of algae attached to stones than, in the pools. On the contrary, in 1955,when the density was high, the pools were utilized as feeding places as in the case of the riffles ; so, some individuals were found staying and feeding there both in the daytime and at night.
"Ayu" (Plecoglossus altivelis TEMMINCK et SCHLEGEL) bas a behaviour to establish a territory, not for breeding, but mainly for feeding. In 1956,from the beginning to the end of June, a number of territories of "Ayu" covered the stone-bottom near Ukawa Bridge at the lower course of the River Ukawa in Kyoto Prefecture, as shown in Figs.1 and 3. The authors have observed in this area that the fish in territories hardly go out of their respective home range, that they do not extend their home ranges immediately after the departure of their adjoining individual from his territory, and that territory-having individuals A and B, given in Fig.2,seem to avoid contact between them. They have also observed that territory having fish drive out all invaders with the exception of those who are in the situations either in driving away their own invaders or in returning from such action. It may be induced from these behaviours that the number of times is remarkably small concerning mutual driving among neighbouring fish (as shown in Table 1). This fact may be note-worthy in territorial life of "Ayu", for, as observed in 1955 in the same river, the fish in territories spend so much time in driving out invaders, that they have no plentiful time to secure their food.
The Kamo River, flowing through Kyoto City, is more or less polluted by the sewage water. In 1941,when Professor TSUDA studied this river, in the neighbourhood of the Kitaoji-bashi (situated at the northern quarter of the city), the river was not yet polluted, and there lived many kathrobic organisms. But in the past 16 years dwellings increased in this quarter and the river water is suffering from the increasing pollution. So I studied in 1956 the fauna of this part of the river, and obtained such data as shown in the right half of Table 2. For the comparison I also studied the neighbourhood of the Misonobashi (2 km up-stream), where the water is not polluted and where kathrobic animals live, which are shown in the left half of the same table. The difference between the two communities was discussed.
1. Average frequency of pecking per hour among 10 individuals in a pen is summarized in Tables 1 and 2. Generally speaking, males surpass females in their absolute pecking-counts, but males tend to peck others somewhat more frequently than to be pecked, whereas the situation is reversad in femaies. Males peck both males and females equally, while females rather prefer the same sex. Those individuals, either male or female, which give more frequent peckings received more peckings from others. The results therefore do not indicate the ordinary hierarchy, but may more reasonably be interpreted as a measure of the activity of individuals. 2. No.1 and No.8 Male, which had occupied the highest rank through their overall peckings before June 14,became less active with decreasing pecking numbers after the date when they begun to incubate the eggs laid by their mates. It is interesting to note that they formed pairs respectively with No.2 and No.3 Female which ranked lowest in their activity. In the later period, No.7 Male became more activated and to consort with No.5 Female. 3. The positions of 10 marked individuals on the two perches and the board are schematically represented in Fig.1. In the period before June 11 on which artificial nest-cases were laid on the perches, the females such as Nos.2,3,4,5 and 6 perched just around No.1 Male, and the other males such as Nos.7,8,9 and 10 took their positions outside of this loose assemblage. Since nest-cases were set, males have been superior to females in their nest occupations. These occupants which tended to change their nest-cases frequently fixed their sites since the middle of June as shown in Table 3. No.1 and No.8 Male with their mates established their territories around their own nestcases (A and C) on the upper perch, and the former pair drove all others from the neighboring nest-case B. The other three males (Nos.7,9 and 4) respectively occupied a single nest on the lower perch. 4. Prior to the establishment of nesting territories, a perch was most frequently occupied by some four resting individuals. Number of birds per perch neither exceeded 6 nor dropped below 2 (Fig.2). Average distance between two neighboring birds was nearly the same regardless of the number of individuals on a perch. In the later period, the upper perch was very often occupied by 2 birds and sometimes by 3 or 4,whereas somewhat more birds (less than 6) were available for the lower perch than before. The distance between individuals considerably increased in case when 2〜3 birds rested on a perch, but remained more or less unchanged for larger numbers (Fig.3). These transitions apparently correspond to the formation of nesting pairs with their territories. The distance relations stated above seems to suggest that the birds in an assemblage maintain a certain minimum distance space between them. 5. Males never stayed anywhere on the board before June 14,while females rested both on the perches and on the board. Although some males also became to perch on the board, the frequency of resting on the perches were by far the greater in males than in the opposite sex. This fact seems to indicate some difference in the space utilization of male and female.
1. The cage used in the present study is a rectangular parallelopiped from, about 250cm×90cm at the base, and 850cm in height. 11 perches of tree branches are set in the cage, and the cage is divided into 9 sections (Fig.1). The names and numbers of the birds are shown in Table 1. Observations were made from Sept.27 to Oct.27,1956,in two periods separated by the transpositions of perches on Oct.10. 2. Interspecific antagonism is found in peckings and avnidances. Their frequencies are shown in Tables 2 and 3,which suggest the existence of the linear dominance-order among species. 3. The vertical distribution of each species observed in the cage is summarized in Fig.2. Apparently the individuals of Psittaciformes are found in the upper region of the cage (Sect.5-Sect.9), the individuals of Columbiformes in the lower (Sect.1), and the individuals of Passerlfomes in the middle. This segregation is probably derived from the differences of the life-forms of each Order. In the same Order, there are two types of interspecific distributions : the separating type, for example, Psittacus eyanocephala and Melopsittacus undulatus observed in the latter period, and the overlapping type, for example, Agapornis roseicollis and A. lilianae. Further observations reveal that the individuais of each species make species-flocks even in the overlapping type and they often exchange the perches (see Fig.3.) The principle of "habitat-segregation", proposed by K.IMANISHI (1941), is thus realized at all times. Only Taeniopygia castanotis and Uroloncha striata often make hetero-specific flocks together.