1)Experiments for analysing the developmental process of plant communities on 1-meter permanent quadrates from 1954 to 1957 are reported. The experimental treatments of the quadrates at the beginning are by exchanging the soi (to exchange the surface soil for the subsoil)and by burning the soil (to burn the surface soil 5cm deep). 2) Burned-soil plot : -The floristic composition (Table 1)shows a yearly change of the dominants : Setaria-Digitaria-Bromus, which differs from that of early stages of a normal successional change in this place : Ambrosia-Erigeron (-Imperata-Miscanthus). The dominance-rank relations (Fig. 1) and composition curve (Fig. 2) show the differentiation of species groups and their development. The biological spectra (Tables2,3) indicate a degree of progression in the succession according to the increase of H, R_1-3 and growth forms except, and a decrease of Th, The spectra according to the summed dominance ratio are more significant than those according to the number of species. 3) Exchanged-soil plot : -The floristic composition (Table 4) of the first year is similar to that of the second year on the burned-soil plot. The yearly change of dominants is Digitaria-Ambrosia-Artemisia-Vicia. The dominance-rank relation (Fig. 3) and composition curve (Fig. 4) seem to show a development of plant population from WILLIAMS'L-type to PRESTON'S S-type, The biological spectra (Table 5) indicate a successional change according to the increase of hypogeals, R_1-3 and 1,and the decrease of the wide spread disseminules (D_2+D_2). 4) Distribution type : -As a stochastic process in the distribution of the number of individuals in a quadrate, the POISSON type related only to the quadrate size a and the geometrical progression type related to a and the number of individuals appeared in a quadrate n are recognized (Table 6 a, b, c). The latter is also called the exponential type in the field of economic statistics. 5) Time effect and area effect : -The distribution type varies as the size of quadrate (Table 7), and varies with time(Tables 8,9)as the geometrical progression type-POISSON type-POLYAEGGENBERGER type-binominal type-normal type. These effects are called the area effect and the time effect respectively by the authors.
As reported in a previous paper the movement of a buccal mass of Oncomelania could be utilized for the examination of its food habits. This movement was named as an"mouth opening reaction of Oncomelania"and a study was carried out on conditions under which this reaction could be smoothly repeated in a certain time unit. The result was as follows. 1. To gain a good result the examination of this reaction should be undertaken with snails in hunger state, and during the time of experiment its body surface, particularly that of its mouth part should be covered sufficiently with a film of water. In ordinary cases such a state will continue to about ten minutes after the commencement of the examination. 2. For the examination of this reaction the optimum PH range is about 5-8.5. In the temperature range of 18-30℃ it can be safely carried out. Within the temperature range of 20-25℃, however, a more suitable result could be obtained. Humidity of air gives no effect on this reaction provided that sufficient water film covers the surface of the snail body. 3. No marked difference was found between the reaction of O. nosophora and that of O. hupensis when both were feeded with soils of the habitat, rice powder and water only. The result suggests that the food habit of both species of snails would be closely related. 4. The frequency of this reaction in a definite time unit was found to be larger with younger snails as compared with that of older ones, which suggests that the intrinsic stimulus for this reaction would be Iarger in the former.
In Izu Peninsula, Histiopteris incisa J. SMITH is found on the western coast particularly both in the Shinden and Yagisawa districts of Toicho, Jinden, Kamo-mura, Kamo-gun, and also in the Kumomi district of Matsuzakicho (Fig. 1). As a result of our research, it has been proved that the Shinden district is the northernmost habitat of this fern in Japan as well as in Izu Peninsula. The mentioned four districts taken together occupy an area of about 1000m^2 ; such a large area of habitat is rarely found in Honshu. In Izu Peninsula, the habitats of this species are near streams, in swamps, by ditches, and in places influenced by springs or dripping water from cliffs. The floristic composition and structure of the community (in this paper, those of Yagisawa habitat are chosen) are presented in Table 1. It is a noticeable fact that so far as the distribution of the fern genera are concerned, these habitats are found on and near the line of annual mean temperature of 15.5℃, which corresponds to the mean temperature of 6℃ in these districts in winter (December, January and February).
Characteristic activities of animals, which are concerned with ebb and flow, have been studied by many authors.(WELSH'38,CALHOUN'44,MORI'45,'50,BROWN et al. '48,'49,'51,'53,'54,'55,'56). Generally, it can be said that both internal and external factors have some relations to the rhythmic movements of animals. From this point of view, observations and experimental analyses of the locomotor activity with the periodic movement of waves were carried out on the sand hopper, Talorchestia brito and the shore sowbug, Tylos granulatus, under natural and laboratory conditions. 1) Sand hopper and shore sowbug are very common along the drift line on the coast of Tottori. They exhibit locomotor activity in the night, but not in the daytime. Their usual positions in sand in the daytime are indicated in Fig. 1. 2) These animals exhibit the following characteristic movement in the night. When the wave advances to the beach line, the shore sowbugs turn to the right or left just in front of the surf and move towards the higher parts of the shore so as to not to be carried away by the retreating wave. When the wave retreats, however, they return to the drift line. On the contrary, the sand hoppers are prompted to jump on the beating wave crest. By such an action, they get to the high parts of the shore. When the wave retreats, they move towards the drift line by jumping up-and-down. By repeating these characteristic behaviors, they do up-and-down migration with waves in the night. These are indicated in Fig.2. 3) Some experimental analyses were also performed to confirm the kind of sense these animals responded to the environments. In the laboratory experiment, the vibration sent out from the electric tuning fork(number of vibration was 50 hertz per minute)was used as the source of mechanical stimuli, the arrangement of which is shown in Fig. 3. The behavior observed in the laboratory experiments are represented in Figs. 4 and 5. It was proved that these animals had special sense to the vibrating stimuli caused by the electric tuning fork. From these laboratory experiments and some experiments executed at the natural habitat, it was supposed that the periodic behaviors in nature were evoked by the vibration of sand or shock given by the waves when they broke down and beat the shore. 4) When kept in the laboratory(first six days under normal day-night conditions and the successive eight days under constant darkness), the shore sowbug persisted its diurnal rhythmic activity for about two weeks, but after that time(again under normal day-night conditions)the activity became irregular and deceased on the 19th day from the beginning of the experiment. Whereas, the same activity of the sand hopper was modified within 3-5 days in the laboratory under normal day-night conditions, and deceased on the 6-7th day from the beginning of the experiment. The normality of the response to the mechanical stimuli mentioned above was decreased in accord with the change in the activity. 5) It was ascertained in the processes of above experiments and observations that the endogenous nature was participated in the exhibition of the diurnal rhythmic activity.
The rice stem maggot, Chrolops orizae MATSUMURA, in summer blood bores near the growing point of the rice plant and injures the developing leaves and ear. After the heading of the host plant the maggot which has eaten the developing ear pupates inside the leaf sheath. The leaf sheath in which the maggot pupates has been observed by some investigators but the results of their observations did not always conform with each other. The author conducted a detailed investigation on this problem. The results are summarized as : (1)In the variety which headed on about the 20th of August, 80 per cent of the pupae of the rice stem maggots were found inside of the top leaf sheath, but in the varieties which head later, the individuals which pupated in the lower leaf sheath gradually increased as the heading date became later. In the varieties which headed earlier than the 20th of August, the individuals pupating in the top leaf sheath decreased as the heading date became earlier, but this relationship was not so close as in the later varieties. (2) When the heading date of the same variety was shifted by means of sowing in different days, the relation of heading date and pupating leaf sheath was nearly the same in many different varieties. (3)In a single variety, the higher the per cent of pupating individuals becomes, the higher the per cent of individuals pupating inside of the top leaf sheath becomes. From this, it is reasonable to conclude that the percentage of the individuals which pupate soon after heading are found at the second or the lower leaf sheath more commonly than in those which pupate later. The pupating date of the maggots differed with the heading date of the host variety. But the duration from heading to pupation gradually becomes shorter as the heading date of the host variety becomes later, that is, in later heading varieties the duration from heading to pupation is shorter that in earlier heading varieties. From the above two facts, it is clear that, in varieties which head later than the 20th of August, the later becomes the heading date, the more the number of individuals pupate at the lower leaf sheath. (4) In early heading varieties, pupation was likely inhibited after a few maggots had pupated. It is reasonably considered that, because in early varieties the number of individuals pupating before the inhibition and mortalty of maggots waiting for pupation were different among varieties, the relation of pupating leaf and heading date was not so close as the late varieties. (5) It was discussed, based upon an example, that if the pupating date fluctuated among years, the relation written in (1) would also differ among years.
During an ecological investigation, field data taken at the time of the survey are of prime importance and should be written in readable from for the purpose of reference. After a scientific report concerning the vegetation surveyed has been published, there remain usually some data not included therein but which might be useful for some other workers. Therefore, to promote the study of plant communities most efficiently. I appeal to the ecologists concerned that the field data taken during a vegetational survey should be copied, distributed, preserved, and open to public. Another important reason is that field data are sometimes lost or misplaced by the worker. Data of geographically separated regions are necessary when comparing their plant communities, even though an individuals reserch may be limited to a certain geographically or politically restricted area. Although many difficulties are met with I earnestly desire its realisation and any opinion will be welcomed.