For the purpose of obtaining knowledge on the seasonal succession of Daphnia pulex, collections were made two or three times a month during 1957〜1958 in the freshwater pond, "Tsujiga-ike", near the Ikeda Campus of the Osaka University of Liberal Arts and Education. The results showed that the population was always monocyclic, while MATSUYAMA noticed that the species was dicyclic in the same pond about 20 years ago. So far as my investigation is concerned, daphnids in this pond began to appear towards the end of November, when the temperature fell to 15℃ ; and gradually increased in number thereafter in spite of further drop of temperature, reaching the maximum population at the end of March. Thence they began to decrease rapidly until they entirely disappeared at the beginning of May, when the water temperature rose to 24℃. Male daphnids were first observed in the latter part of February ; and after gradual increase in number, they were found to make up 14 per cent of the total number of individuals towards the end of March. In the middle of March, ephippial females were likewise found abundantly, and at the beginning of April, nearly all the individuals in the pond seems to be turned out to this state. Laboratory experiments were made on the resting eggs in various conditions of ephippia. There was not a single resting egg collected from the pond in autumn to hatch at temperatures of 30℃ and 2℃ respectively, while some of them were found to hatch at 20℃ or 15℃. Those collected in spring could not hatch at 20℃ and 2℃ respectively, though no fewer than 84 per cent of them could hatch at 12℃ in less than a month. When stored in an ice box for six months, a few of them could hatch at 15℃ or 20℃. However, if they were left in a glass to become dry under natural room conditions, they could not hatch. Accordingly, it may be concluded that the hatching ability of these resting eggs is reduced at temperatures above 30℃ and under drying conditions and that the longer is the period of storage, the weaker becomes the hatchability. Daphnids were bred in 250cc of BANTA'S culture medium at different temperatures as well as under other favourable conditions. The results showed that within six hours all the individuals, both adult and young, died at 30℃ and 25℃. At 20℃, however, they become mature within the shortest period of time, producing thereafter parthenogenetic eggs at the shortest intervals and with the largest in number. At 2℃, though some perished, a considerable number of them still survived, and a part of them continued growth within some 40 days, even producing parthenogenetic eggs a few times. According to TAUSON'S experiments, the range of temperature for the life of Daphnia pulex is 10〜30℃, its optimum range for parthenogenesis being 15〜25℃. My experiments as well as field observations, however, show that the living range in the "Tsujiga-ike" population falls between 2℃ and 23℃, its optimum being between 7℃ and 17℃. Generally speaking, it is believed that, as shown by TAUSON'S experiments, the males and resting eggs occur when the temperature changes from high to low degrees. Contrary to his opinion, however, from my results obtained experimenmlly and from field observations, it was confirmed that the males could appear when the temperature changed from low to high. The adult females were found to produce their ephippia without being fertilized by the males, such a way of ephippium production having repeated twice or more. When they were collected from the "Tsujiga-ike" and bred in the laboratory, the ephippial females mostly perished soon after their ephippia were cast off. However, out of 240 individuals examined, 46 again produced ephippia and three consecutively three times, while eight individuals again laid parthenogenetic eggs after they moulted. Therefore, it may be supposed that the remarkable depression of population at the beginning of April.
1. From the materials concerning the occurrence and distribution of pelagic larvae and the drift of youngs, the main spawning area of the porcupine puffers, Diodon holacanthus LINNAEUS, immigrating to the Japanese waters was estimated to be found in the coastal regions of Luzon, Formosa, the Yaeyama Islands and their vicinity, while their spawning season to extend over April to July(Fig. 1 and Table 1). 2. A discussion was made on the migration of young porcupine puffers in the surrounding waters of Japan, with particular reference to the influences upon their drift of the main streams of the Kuroshiwo and the Tsushima Current as well as the drift currents generated by the northwest monsoon winds, and maps showing their probable migration routes were presented. (Figs. 2 and 3). 3. The migration of this Diodontid fish to the Japanese waters may be classified into the "propagative migration", i.e., a migration of a passive nature during the planktonic or pelagic juvenile stage, and so far as the fish schools that entered into the Japan Sea are concerned, their migration can be termed as "abortive", for most of them are considered to be stranded to perish on the seashore during the stormy winter days.
It is supposed that the main foodstuff of Oncomelania snails should be the diatoms and the other algae contained in soil, because they usually take soil particles into their mouth incessantly in their natural habitat. Several specimens of the surface soil were taken from the four different habitats of Oncomelania snails in Yamanashi Prefecture and examined for
The woolly apple aphid, Eriosoma lanigera HAUSMANN, is one of the most important pests of the apple tree in Japan. This insect attacks the roots as well as the upper parts of the trees. Above the ground it is found mainly on the trunks, limbs, and twigs in wounds caused by pruning or cultivating implements, and wherever the bark is tender. Occasionally, the aphid forms colonies on the fruit stems and in the calyx ends of apples. Facing the biggest infestation mentioned above by the said insects, it was necessary to have introduced into apple cultivation the strenuous parasite, Aphelinus mali HALDEMAN, in order to regulate the aphid populations. After the application practice of this parasite, it became of minor importance up to about 1946 when they began to use DDT and parathion in general to control the various pests in the orchard. For several years in the past, however many reports have claimed a tremendous increase in the infestations of the aphid in these orchards sprayed with DDT. This increase has been attributed in most instances to the destruction of the building of the parasite population. From the above reason, it is desirable to explain the relation between the two species of the host and parasite. In the present article, an account is given of the investigation largely carried out in 1956〜57 on their bionomics of the interaction under natural conditions, the results of which are compared with those recorded in an orchard applied with DDT. 1. Observations under the fluctuating environmental conditions in the net house during the course of parasitism over a period showed that at first Aphelinus parasites came from places where they had completely situated to each other, and parasitized to Eriosoma aphids which had just began to develop the population growth. Then when some of the aphid population migrate seeking another twig and to avoid enemies, Aphelinus also soon pursue them successively.
Using 31 typical varieties of sesame introduced from nine countries including Japan as material, experiments were carried out on the treatments of high temperature (in Vinyl house), long-day (in the day time, by natural exposure, at night illuminated all night 30 days from germination), short-day (exposure of eight hours per day 9A.M.-5P.M.) and check plots (cultivation under natural conditions). According the results of the experiments the effects of these treatments on the growth of sesame were as follows : 1) As to the plant height, there was the same tendency at long-day and at high temperature treatment, but in general the growth of the stem of the heat plot was more conspicuous than that
From the results of the investigations during six years from 1953 to 1958,the writer sought for the decisive factors for the establishment of a Phragmites community among the abiotic habitat in a reed swamp, situated in Asuwa Subprefecture, Fukui Prefecture. The swamp lies at about 10m above sea-level. It has developed around a small pond by the sudden and striking increase of spring water after the Fukui Earthquake in 1948. The swamp is invaded by Phragmites all over, but four facies are recognized by the dominance of the following species respectively ; Phragmites communis, Zizania latifolia, Scirpus preslii and Alnus japonica (Fig. 1). It is noticed from the three years observations that the interspecific competitions in the Phragmites and the Zizania communities are so serious that an almost pure stand of each plant has been established and annuals have substantially been excluded from it. From the distribution of component species and their successional trends in this swamp the writer came to the following conclusion that, the water depths (Tables 1 and 2), the scarcity of soluble phosphorates and the excess of active alumina in the soil (Table 4) may be responsible for the occurrence of these, especially the Phragmites communities. Furthermore, he assumes that actual acidity, organic matter content as well as mechanical texture of soil (Tables 3 and 4) are only indicative, but some critical conditions caused secondarily by them are essentially effective to the establishment of the swamp communities.
1. A quantitative survey of the aquatic insects in seven tributaries of the upper region of the Chikuma River has been undertaken at 22 stations by members of the research group of Chikuma from March 1957 to January 1958. 2. The number of species collected from these stations was 53,among which 16 were Trichoptera, 12 were Ephemera, 6 were Diptera and the rest belonged to Coleoptera and Neuroptera. 3. The dominant species in the upper region of the river were found to be Ephemera, but in the lower region Trichoptera species were abundant. When the type of river becomes "Bb" the nymph of Potamonthus kamonis took the
I studied the effluents of three copper sulphide mines, Tateri Mine and Kawamata Mine in Nara Prefecture and of the Imori Mine in Wakayama Prefecture, with regard to their effect on stream organisms. The water insects were collected quantitatively at several stations of the rivers which receive the mine-water(Figs. 6,7,8,9). The effect of the effuents is very distinct. The water insects decrease in species number as well as in individual number with the distance from the source.
The survey was made at three points in each station using 1 m^2 quadrate. As periwinkles show positive phototaxis and inhabit on the surface of the substratum, the qaudrate method was available to measure their density even on a stone wall with many small holes. Chlorinity was determined by means of AgNO_3 and K_2CrO_4 and shown in mg per litre. There are many periwinkles along the O-hashi River amounting to 100〜130 individuals per 1m^2,and 60〜75 inidividuals were found in the west of River Tamatsukuri, but in the west of River Kimachi only less than five individuals were found. Though the substratum seems to be favourable to the inhabitation of periwinkles, none appeared in the west of Aika situated on the northern coast and also at the western coast. It seems that the above phenomena may be due to the muddy sand carried by the stream of River Hi-i, and it should be the same at Nogi where the River Nojiro flows into the Lake. In Lake Nakaumi, periwinkles are less than 42 in number at the station observed and are influenced by the high chlorinity. Judging from the laboratory experiment the upper limit of
Um ein Zentrum der modernen Pflanzensoziologie bekannt zu machen, das aktive Arbeit leistet und damit reiche Wirkungen erzielt, mochten wirtiber die Bundesanstalt fur Vegetationskartierung und deren Grunder und Leiter, prof. Dr. RKINHOLD TUXEN, einen kurzen Bericht geben. Die Bundesanstalt (fruher : Zentraistelle) fur Vegetationskartierung wurde 1939 in Hannover als pflanzensoziologisches Fachinstitut fur Forschung und Anwendung von Prof. TUXEN gegrundet und 1943,um der Kriegafackel zu entgehen, nach Stolzenau a.d. Weser evakuiert. In diesem schonen, ruhigen Flecke hat sich das Institut durch viele nicht zu iibertreffende Erfolge weiter entwickelt und starke Impulse in die ganze Welt susgestrahlt. Die wissenschaftlichen Fachgebiete der Bundesanstalt umfassen heute drei Abteilungen : Foratliche Soziologie, Grunland-Soziologie und Landwirtschaftliche Soziologie mit zur Zeit insgesamt 16 wissenschaftlichen Mitarbeitern. Der technische Stab vereinigt 22 Fachkrafte fur alle pflanzensoziologischen Arbeiten wie Sammlungen, Tabellenbearbeitung, Kartographia, Bibliothek, Archiv, Dokumentation and Schriftleitung sowie Verwaltung. Der schonste Eindruck der Bundesanstalt auf einen Gast ist die ideale Zusammenarbeit der begelsterten Assistenten und der sorgfaltig auagebildeten technischen Mitarbeiter unter der sicheren und verantwortungsbewubten Leitung von Prof. TUXEN. Sie bilden alle ein vielseitiges gut ausgewogenes und anpassungsfahiges Team, das alle wichtigen Gebiete der theoretischen und angewandten Pflanzensoziologie und deren Ausstrahlungen in die Nachbargebiete mit Hiagabe bearbeitet.