1. In the estuary of River Tatara, Fukuoka, the mono-specific populations of a burrowing fiddler crab, Ilyoplax pusillus DE HAAN, are usually found on the river-bed of muddy or sandy sediments. By the quadrat census, it was made clear that the distribution of the nests of the crab becomes more and more uniform with the increase of the population density. This fact indicates that the interaction among individuals is promoted at highdensity. 2. The interference between two individuals was investigated experimentally. At first, one individual was introduced into a wooden box(10×10×10 cm). After the first individual had burrowed its nest, the second one was introduced into the same box. Then, the distances between the nests of them and the corner of the box nearest to the first individual were measured. The index of the degree of interference(I)between the two individuals was calculated as follows : [numerical formula] Four sex combinations were used in the experiment ; the first individual was a male and the second one was also a male(♂_1-♂_2), ♀_1(the first individual was a female)-♂_2 (the second one a male), ♂_1-♀_2 (the second a female), and ♀_1-♀_2. The curves of the value "I" plotted against the distance from a corner show that the male has a repulsive character, while the female has attractive and a weak repulsive character. 3. The distribution of the nests in the natural habitat was plotted on a map, and the distance between each nest and its nearest neighbour was measured. The degree of interaction among individuals was measured by comparing the frequency of the shortest distance mentioned above with that of the random one calculated by MORISITA'S method as follows : I=Calculated frequency/Observed frequency. This value "I" was calculated at various nest densities. The curves of value"I"show that the type of interference reveals the repulsive relation among individuals. However, the shape of the curve is constant irrespective of the increase of population density. 4. By comparing the results mentioned above with the interference types observed in the experimental boxes, it is concluded that the appearance of the repulsive type in the distribution of nests in the natural habitat depends mostly on the active character of the males.
With cut leafy tops of a xeric-hygric series of mosses, consequently in the conditions independent of ecological factors such as habitats, growthforms, water absorption, etc., the relations between xeromorphism and transpiration were investigated ; special references were taken to the transpiration rate and the water deficit velocity under the laboratory conditions. Under the following conditions in the laboratory, the leafy tops continue to transpire their water for more than 40 minutes to an hour with little reduction in the rate until the hydrability reaches itself to about 50 per cent(in endohydric mosses)or less than 30per cent (in pollacauophytes)
This paper deals with the results of the preference test between cabbage and radish for oviposition by the cabbage butterfly. As the test animals, the newly emerged adults grown on the cabbage and radish leaves were employed. The results are summarized as follows : (1) The female butterfly lays eggs most vigorously on the host plant at 2 to 3 days after emergence, but this behavior ceases at about 7 days after emergence (Table 1). (2) Both the adults grown by the cabbage and the radish show the same tendency to prefer radish to cabbage for oviposition (Table II). (3) No decided difference can be found between both strains in the ratios of the numbers of eggs layed on the cabbage and the radish leaves.
In the previous report the author classified the sesame varieties based upon their photoperiodic responses into five groups, viz., 1) a group highly sensitive to both short-day and long-day conditions, 2) a group more sensitive to short-day, while less to long-day conditions, 3) a group less sensitive to short-day, but more to long-day conditions, 4) a group low sensitive to both long-day and short-day conditions, 5) a group sensitive to long-day conditions only. The present paper gives the results of tests carried on at the Shikoku Agricultural Experiment Station, Zentsuji, in 1955. The latitude of this place is 34°13′N. Different days were used in the growing of 30 sesame varieties obtained from eight countries, where the following daily periods were maintained from July 10 to August 10 : a) 8 hours per day, b) natural conditions, and c) in the day time, by natural exposure, at night illuminated all night with two bulbs of 100w. from the distance of 1.5M. These were sown on June 30 and after treatment their growth was put to their natural conditions. The effect of the photoperiodic responses on the growth of sesame varieties belonging to the above five groups and the results of the experiments are summarized as follows : 1) The varieties of sesame which were introduced from Africa, Indonesia and a part of India did not ripen fully by the long-day management, which hindered to procure ripened capsules. 2) The color of corolla showed some change by the long-day managemen ; and as far as the varieties of high sensitivity to both long-day and short-day are concerned, the color of the flowers was recognized to have a tendency to change from light to dark. It is presumed that temperature has a close bearing as is inferred that by the long-day management it bloomed in the low temperature of October. 3) The shapes of the leaf blade are variable in general ; in the best time of growth, among the varieties which have a compound was or palmete simple type of leaf, under the long-day management, the degree of lobation in a leaf was remarkable ; under the short-day management, on the contrary, lobation was less found. 4) With regard to the leaf type, as a general rule, most of the group which is highly sensitive to both short-day and long-day conditions, in the period of vegetative growth, a fusses the ternate compound leaf ; while the groups of low sensitivity to both long-day and short-day conditions, of long-day conditions of low sensitivity to short-day, while low to long-day conditions were generally of simple leaf type. 5) The number of flowers per axil also changes : under favorable nutrition the number of flowers per axil was peculiar to the variety, and under unfavorable environment a decrease wasvaried. According to the short-day management the decrease of number of flowers per axil was recognized in general. 6) The short-day management capsule growed short and small ; the number of seeds per capsule diminished, and the seed, both in its shape and size showed some variation.
(1) Investigations on the aphid population were made in a cabbage field at Nogi, Matue City, from late April to early June in 1956. The species recorded during this period were Myzus persicae, Brevicoryne brassicae and Rhopalosiphum pseudobrassicae. The last mentioned species was rare. (2) There was a remarkable difference in the pattern of distribution of aphids on a cabbage leaf between M. persicae and B. brassicae : In the case of M. persicae the aphids were scattered on a part of the leaf (sometimes all over the undersurface of the leaf), while in the case of B. brassicae the colonies were built up tightly and these were scattered. (3) It seems that the distribution of the aphid in a cabbage field had a correlation with the direction of the prevailing wind in the spring. (4) M. persicae shows a preference to the leaves at the lower part of the plant. On the contrary, the colony of B. brassicae is apt to build up in the upper part of the plant, excepting the part at which the leaves are bulbed up. (5) Winged forms of M. persicae came flying to the cabbage field from the end of April, but the population growth was restrained by severe circumstances until about the 10th of May. On the plants which aphid populations were growing favorably, these were sudden increases of aphid numbers at about the 20th of May, when many aphids reached maturity and many individuals of the new generation were produced. (6) Winged forms of B. brassicae did not seem to fly to the cabbage field before the beginning of May. The populations of this species also made sudden growth at about the 20th of May on the plants which the aphid populations continued to grow smoothly from about the 10th of this month. On the plant having a large population at the 4th of June, many colonies were built up in the lower part and on the part at which the leaves are bulbed up as well as in the upper part. (7) In both species there were some number of individuals which were attacked and swelled up by parasites, when the investigation was made on the 4th of June.
The influences of the population density might be explainable by some factors such as shortage of food, interference among larvae and the biologically conditioned environment. This study is intended to clarify the effect of the conditioned food upon the larval development of the almond moth, Ephestia cautella WALKER. The conditioned food used in this experiment is the rice bran containing the faeces of larvae. The results of this experiment are as follows. The duration of development in the immature stage is prolonged, the emergence of the moth occurs by degrees in a long period, and the percentage of emergence and the size of the moth are decreased with increasing the quantity of faeces added. These results resemble that of the effect of population density described in the author's previous paper(TAKAHASHI, 1956). In the present experiment, the conditioning of environment is only a factor producing to above results, and the amount of food as well as the available space of larvae are ignored. Therefore, it is assumed that the conditioning of environment plays a greater role to produce the general effect of population density.
1) In spite of the great importance of CO_2 concentration of the air as a limitting factor of photosynthesis, little is known about its distribution in plant communities. The present paper deals with the vertical distribution of CO_2-concentration of the air in some plant communities in the Tokyo district and of the subalpine region of Mt. Senjo. 2) The CO_2 contents of the air at the ground surface layer were about 1.0-1.8 mg/L in the herbosa, 0.67-0.75 mg/L in a crop field in Tokyo, about 0.9-1.3 mg/L in the subalpine herbosa, and 0.6-0.9 mg/L in subalpine silvae in the daytime. Whereas in the leaf layer they were 0.55-0.65 mg/L, 0.52-0.65 mg/L in the herbosa and a crop field in the Tokyo district, 0.6-0.7 mg/L in the subalpine herbosa, and 0.55-0.65 mg/L in the subalpine silvae.
Simultaneous horizontal haulings of several different depths were made on the sardine spawning ground off Noto Peninsula, Japan Sea, in the spring of 1955. Observations on the plankton samples obtained have led to the following. Of the sardine eggs belonging to the same age category, those eggs floating in the upper layers are more advanced in development than those in the deeper layers(Table 1). This phenomenon is inconsistent with the view that in sea waters the pelagic sardine eggs would be continuously mingled to a great extent by large-scale eddy turbulences and their floating depths would be disturbed incessantly and irregularly. On the other hand it is supposed that they would for some reasons be kept rather unchanged in their relative positions to each other during the embryonic development and that based upon the vertical gradient in water temperature in the sea(Fig. 1), the above-mentioned difference by depths in the rate of development would result.
1) Under the experimental conditions, the plus interference (aggregative tendency) is seen among the individuals of a goby, Gobius abei. The habitat preference of the indviduals is much affected by the interference. 2) Different degrees of the interference are seen with the different conditions of the environment. 3) An equation based on MORISITA'S "environmental density theory" has been employed to find the relationship between the degree of interference and the environmental conditions. 4) The expected values of frequency distribution of individuals based on the equation mentioned above coincide well with the observed ones. 5) The environmental density has been proved to be constituted by the product of the "coefficients of the environmental densities" as claimed by MORISITA. 6) From these results, it is concluded that the environmental density theory is sufficient to be applied to the habitat preference and spatial distribution of the goby, and possibly also of other animals.