The author gives the results of a survey made in about two years from late July, 1952 through late September, 1954 on the diurnal and seasonal succession of the natural population of Drosophila inhabiting a latifoliate forest in Anjo City, Aichi Prefecture. The collections were made with traps baited with fermenting fruits. In the collections made at regular intervals, the author obtained 17266 specimens belonging to 21 species(Table 1). The following four types of diurnal activity(Fig. 1)were discriminated : A : With a high peak in the morning and a low peak in the evening. This is the commonest type of diurnal activity. B : With two peaks at sunrise and sunset. D. auraria. C : With a peak in the evening. D. coracina. D : With a peak in the midday. D. subtilis. The following four types of seasonal activity (Fig. 2) were recognized : Spring-autumn type : D. lutea, D. auraria, D. rufa, D. transversa(D. nigromaculata), D. sp. 1 of robusta group, D. sutlilis and D. immigrans. Summer type : D. coracina. Autumn type : D. suzukii(D. pulchrella), D. melanogaster and D. bizonata. Winter type : D. sp. 1 of immigrans group. The seasonal change in the composition of the natural population was investigated, and distinguished according to the following criteria (Fig. 3) : total number of the collected specimens, number of specimens of the dominant species, number of species, percentage of specimens of the dominant species, variance of percentages of the individual species, constants "a" and "b" of the formula of geometrical series, PARETO constant (α) and correlation coefficient of population between the successive periods. The following phases were recognized : 1. The hibernating phase(early November through early May) : Population of low density monopolised by D. sp. 1 of immigrans group. 2. The first active phase(early May through early August) : Population of high density dominated by D. lutea and D. immigrans with mixture of D. auraria. 3. The summer resting phase(early August through late August) : Population of low density dominated by D. auralia in the morning and evening, and by D. corarina in the daytime. 4. The second active phase(late August through early November) : Population of high density consisting of many species, the dominant species being D. melanogaster, D. lutea, D. auraria and D. bizonata. From these findings the author considers that in the animal population composed of closely related species, if they are highly motile and broadly adaptable, co-existence of them in the same environment as well as habitat-segregation, is very common.
Quantitative studies on the diatoms which attached to the cultivating lavers(Porphyra tenera)collected from various parts of Japan were carried out. Synedra gracilis was dominant in almost all laver fields while a few of Licmophora flabellata and Achnanthes subsessilis were found in only some inland seas. S. surperba was found often in association with S. gracilis.
Antheraea yamamai is an univoltine insect, the life cycle of which is as follows : In the fall the egg enters into hibernation, when every organ of the embryo has developed in appearance almost to the full. Owing to the warm spells from March to April, it gradually completes its developement, until at last it hatches in May. After Ecdysis four times, the hatched larva becomes perfectly mature and begins to cocoon-in the Matsumoto district it takes usually 45〜50 days from hatching to cocooning. Four to five days are required to complete cocooning which is followed by pupation three to four days thence forth. As regards emergence, it commences 20〜25 days after pupation and continues as long as four months viz. from July to October as is exemplified in table I. Needless to say, silkworms are reared in a house where the air is to some extent conditioned, so that they keep step with each other in ecdysis, cocooning, pupation and emergence, viz. every metamorphic phase occurs rather simultaneously. Antheraea yamamai, on the contrary, being reared outdoors, the enviromental condition is not equal everywhere in the Quercus trees, that is there are wide differences between the upper layer of the tree crown and the lower one, not only microclimatically but in the quantity of the fodder as well. Therefore even though the worms hatch simultaneously they do not keep step in ecdysis, cocooning, pupation, and emergence but sometimes differ by several days in the same metamorphic phase. However, the emergence of A. yamamai is extremely protracted even if the above-mentioned irregularities are considered. Moreover the daily fluctuation of emergence shows that the emergence does not occur evenly during the period but that there are two peaks, viz. the minor one is from late July to early August and the major one in late September. In order to reveal the cause of this noteworthy phenomenon, the writers observed the pupae analytically just before the beginning of emergence, with the result that, concerning the imago differentiation, there are three kinds of pupae, that is, the one is those that have already completed their imago differentiations, the second is those that show no trace of imago differentiation but enter into aestimation-this aestivation cannot be broken even if they are put under a temperature favorable for emergence such as for instance, 25℃-and the third is the intermediate ones who do not enter into aestimation but the imago differentiations of which are sluggish.
The vertical distribution of two intertidal gastropods, Nodilitorina granularis and Littorivaga brevicula, and the interaction between them were studied. These two periwinkles are one of the most common inhabitants of rocky shores in Japan. In the vicinity of the Seto Marine Biological Laboratory, the ranges of vertical distribution of these two species are clearly separated from each other. That is to say, N. granularis inhabits the upper part of the intertidal zone, and L. brevicula occupies the area just beneath it. One of the examples is shown in Fig. 1. If. the snails beionging to one of these two perlwinkles are removed experimentally from their native habitats, this vacant area is soon reoccupied by the individuals of the same species or remains vacant at least for 2 days, and is never intruded by any other species. These facts seem to show that this clear separation (so-called "habitat segregation") is not caused by the interaction between these two species, but probably by the actions of some external environmeats. This supposition may be supported by the fact mentioned below. At the rocky shore near the Misaki Marine Biological Laboratory, the mode of distribution is somewhat different. Here the areas occupied by these two species overlap, as is shown in Fig. 2. The cause of this discrepancy seen between the Seto and Misaki snalls will probably be attributable to the difference in the phyaical environmental conditions such as substrata or waves.
1. Pollen analysis was carried out on Meiocene lignite samples obtained from the Nishitagawa coal field, Yamagata Prefecture. 2. Examining the pollen of Alnus and 36 other kinds of tree, a comparative study was made on the pollen flora in each bed. 3. Such pollen grains of extinct plants as Sequoia, Taxodium, Cunninghamia, Liquidambar, and others were found most predominantly in the Aburato coal bearing bed. 4. As the pollen flora of the plants of the temperat and sub-tropical zones is found abundan, it may be said that the environment of that age was similar. 5. The pollen speicies observed in this analysis are similar to those of the Mogaml and Okitama coal fields, both of which belong to Pliocene. Therefore, it is concluded at least that the same kinds of tree as the present have survived since the beginning of Neogene-Tertiary.
Fundamental investigations on the cultivation of Paramecium caudatum were carried out in a closed culture system with the baked lettuce infusion and certain substances that are necessary to increase the maximal density and the fission rate. 1. The maximal density varied with the number of paramecia inoculated at first. This maximal density could be raised by the addition of a medium in which the bacteria had propagated sufficiently. 2. The maximal density and fission rate could be increased by the addition of an orange pericarp extract to the medium at the rate of 0.5 per cent, but the extract was effective only when there was a sufficient number of bacteria necessary for the living of paramecia. It was ineffective when the density of bacteria decreased to a certain level. 3. Ascorbic acid and other organic acids(citric acid, succinic acid, and tartaric acid)were ineffective.
To study the influence of temperature on the soaking of seeds, the writer used the kidney bean(Phaseolus vulgaris L.). The seeds which absorbed various amounts of moisture by placing in desiccators or moist chambers at room temperature were soaked in tap water filtrated through the ion exchange resin and kept at temperatures of 0°, 10°, 20°, 30° and 40℃. for periods varying from 2 to 48 hours. At the termination of the soaking period, the water was drained off and the seeds were placed for germination tests on moist filter papers in cabinets held alternately at 20℃. for 16 hours and 30℃. 8 hours. As a result of soaking in water for 2 hours, the seeds which contained more than 5.7 per cent of moisture before soaking in water showed a decrease in germinative capacity at low temperature and normal germination at high temperature. On the other hand, the germination of dry seeds was perfectly inhibited at high temperature but increased at low temperature. This increase of germination occurs as a result of the slight absorption of water during the soaking at a low temperature for 2 hours. Dry seeds soaked at 0℃. for 8 hours were perfectly deprived of their germinative capacity. In the next experiment, the seeds with large moisture contents were soaked in water for 24 or 48 hours. Seeds soaked in water at temperatures lower and higher than 20° and 30℃ for 24 hours showed a pronounced decrease in germination, but those soaked in water at 20℃ and 30℃ for 24 and 48 hours still had their germinative capacity. The soaking temperature and the moisture contents of the seeds are the important factors in soaking injury.
In a village of Miyagi Prefecture, epidemiological studies on the hookworm were carried out from 1954 to 1955. The incidence of human infection was found to be relatively higher in percentage on residents working in fields under cultivation and lower in those who had no or seldom chance of working in fields. Among the latter were included babies, children, nurses, care-takers and students. The infection of hookworm is thought to be remarkably effected by the mode of life, the relation of the mode of life to the contaminated area is of great importance to the infection. By the treatment with tetrachiorethylene 216 cases were found to discharg hookworms. Twentythree or 12.2 per cent of them were infected with Ancylostoma duodenale DUBINI, whereas 80 or 42.6 per cent with Necator americanus STILES and 85 or 45.2 per cent with both species. Of the total of 5279 specimenus of hookworm 4481 proved to be A. duodenale and 798 N. americanus.
A field survey of the root-knot nematodes was undertaken in the northern part of Hokkaido. The results so far obtained during the period of May-November 1955 are as follows : 1. Wild plants of 46 species covering 19 familles on which more or less galls were observed, were collected at 13 localities ; no Gramineae was infected(Table 1). Among them, 16 species which had not been recorded in earlier reports relating to the hosts of Heterodera marioni, now a synonym of Meloidogyne spp., were included. These are indicated with asterisks in Table 1. 2. Soy bean, azuki bean, pea, red clover, pyrethrum, burdock, Jerusalem artichoke, red pepper, potato, carrot, sugar beet and flax were observed to be commonly infected by the root-knot nematode. 3. All of the infected plants disclosed the presence of only a single species Meloidogyne hapla. 4. No gall was found on the roots of 14 species of plants including 11 species of the Gramineae grown inside the heavily infected sites. This suggests that these plants are not hosts of M. hapla. A list is given in Table 3. 5. The plantain, Plantago major var. asiatico, P. lanceolata and the dandelion, Taraxacum platycarpum, have the widest distribution and bear exaggerated galls when infected. These weeds were of use to confirm the presence of the nematode in the soil. 6. M. hapla was frequently discovered in characteristic soils such as peat soil, acid soil, clay soil and acid beavy clay soil ; these soils occupy a comparatively large part of this region. 7. The pyrethrum galls of nearly the same size were inoculated to 8 species of plants grown in pots. It seems that the size of the newly produced galls is characteristic to the species of the host. Fig. 3 shows the size of the galls of pyrethrum, dandelion, soy bean, peanut and potato, from left to right. M. hapla failed to attack barley, wheat and maize. 8. Plants infected by this species have extensive root proliferation and always several lateral roots just above the gall.
1. Twenty-three series of correlation coefficients obtained by the reciprocal treatment of catch in every year are classified to four types.(Refer to Fig. 1)2. Correlation coefficients of the association between the successive years are shown in Fig. 2. The depressions of the curve are equivalent to the turning points of the type in Fig. 1. 3. It is presumed that the fish composition which maintains the condition immediately before interruption of fishing failed to return to the beginning condition, because the series of correlation coefficients from 1952 to 1954 are similar to those from 1942 to 1943. 4. The fish species which have effect on the change of composition are, sea bream, white croaker, black croaker, sharp toothed eel, ribbon fish and butter fish, and they are distributed in main fishing ground and caught by trawllers. 5. Concerning the organizing process of the fish association, the law of geometrical progression can be applied in 1941,and such a linear relationship was not recognized in other years. I should like to consider that the demersal fish association in 1941 showed the maximum development.
In previous reports I have mentioned that the soil used after the forage crop cultivation promotes soil aggregation, and that the amplitude of soil moisture and soil temperature in the upper parts of this soil is very remarkable as compared with that under wheat-sweet potato cultivation. In order to get good germination and good early growth of crops in the soil used after forage crop cultivation, such as maize and soybean, we must change the depth of seeding according to the kinds and varieties of them. In this paper, I mention about the difference of germination and early growth of upland rice in the soil used after the forage crop cultivation and compare this difference with that of the soil used after the wheat-sweet potato cultivation. The experiments were carried out from May to July in 1954,the results are as follows. (1)The germination of upland rice in the soil under the 5 years forage crop cultivation was better than that in the soil used after the 5 years wheatsweet potato cultivation. The large amplitude of soil moisture as well as that of soil temperature gives good effect on the germination of upland rice. The best depth of germination was 1-5cm. (2) The maximum seeding depth of upland rice was 15cm. (3) In connection with the growth after its germination, the best depth of seeding was 3cm. (4) The germination of upland rice in the soil used after F. elatior L. cultivation was best, which was followed by that in the soil used for T. repens cultivation. (5) With respect to the amplitude of soil moisture as well as that of soil temperature, the soil used after the forage crop cultivation was more remarkable than the check plot. Its degree was more remarkable in the soil used after F. elatior L. than in the soil used after T. repens cultivation.
1) Investigations have been carried out on populations of nymphs of the tick, Haemaphysalis bispinosa NEUMANN by two collecting methods using cotton-flannel in a pasture at the foot of Mt. Sambe in Shimane Prefecture. One of the two methods was dragging of flannel for some distance and the other was rubbing vegetation on piece of flannel. 2) The same area in the pasture was investigated by both methods at the end of April, 1953. Collecting efficiency of ticks by the rubbing method was much greater than by the dragging method. The regions where many ticks were collected, however, did not necessarily coincide with both methods. 3) It seems that the collecting effciency of ticks by flannel was greatly influenced by temperature in the early spring. Ticks were collected more abundantly in fine than in fine than in cloudy weather, when the maximum temperature in the cluster of grass rises occasionally above 35℃. 4) A laboratory test was conducted on the reaction of nymphal ticks to heat, in which temperature was raised with the rate of 1/4℃. per minute. The test ticks reacted actively to temperatures above 35℃. 5) The rubbing method was used twice in the same area at the end of April and the middle of May, but different results were obtained on the distribution of nymphal ticks.