The ecological studies of aquatic fungi were carried out in the mesotrophic Lake Yamanakako from August to November in 1957. 1. The zoospores of aquatic fungi showed considerable variation in amounts, with the maximum in autumn and the minimum in summer and late autumn. 2. The seasonal fluctuation of the fungi differed according to species, i.e. Aphanomyces sp. flourished in summer, and the genus Saprolegnia in autumn. Pythium sp. was obtained both in summer and autumn. 3. The zoospores of aquatic fungi were distributed uniformly from the surface to the lake bottom in autumn, while they were seen only in the epilimnion in summer. 4. The aquatic fungi of the bottom deposit were rich in autumn in number of species. Pythium sp. was the preponderant member in every season. 5. The standing crop of the fungi differed between the Main and the Hirano basins according to diversity of their limnological natures.
According to the literatures concerning this subject, Plagiogyria adnata (BL.) BEDD. is distributed in India (southern part?), Thai, Malaysia, Java, Philippines, China (southern part), Formosa, Ryukyu and Japan. In Japan, this species is distributed in Kyushu, Shikoku and Honshu (Yamaguchi, Nara, Kyoto her southern part), Wakayama, Mie, and Shizuoka Prefs. and Isl. Hachijo), Shizuoka Pref. being the northernmost habitat of this species. In Shizuoka Pref., the habitats of this fern are now found in (1) Mikkabi, Mikkabicho, Inasagun, (2) Kamino, Tenryu City, (3) Itasawa, and (4) Ganshoji, Kakegawa City, (5) Iriyamase, Kitomura, Ogasagun, (6) Yainaba, and (7) Hara, Fujieda City, (8) Kurishima, and (9) Matsuno, Shizuoka City, (10) Kiriyama, Amagiugashimacho, Tagata-gun, (11) Numanokawa, Kawazucho, Kamo-gun (cf. Fig. 1). Our research has proved that the habitat in Fudodani, Hara, and Fujieda City forms the largest and the northernmost community in Shizuoka Pref. and Shizuoka City is the northernmost limit of this fern in Japan as well as in Shizuoka Pref. Some environmental factors in the northernmost habitats of this species are as follows : At present, all habitats of this fern range from 34°44' to 35°06' N. lat. and are found from ca. 50m to ca. 420m alt. It is a noticeable fact that these habitats are found on and above the line of the annual mean temperature of 14℃ which can be safely said to be the limit in annual mean temperature for this fern. This fern belongs to the warm temperate zone of Shizuoka Pref. as well as in the other regions of Japan. The vegetation of most of these habitats is the laurel forest in which Shiia dominates. As an example of floristic composition and community structure, especially the habitat of Fudodani, Hara and Fujieda City are presented in Table 2. This fern is always found in a shady and moist place under the forests. pH of the soil in these habitats was from 5.4 to 6.4 and this measurement is almost identical with the study of SHI^6). Therefore, this fern can be said to belong to the acidophilous plant. The kinds of substrata in which this fern grows are basalt, andesite, sandstone, shale, conglomerate, gravel bed, humus and their disintergrated products.
The distribution of the individuals of the almond moth, Ephestia cautella, within the layer of rice-bran which was given as their larval food was observed in relations to their stage of development and to their population density, under the experimentally controlled condition of 30℃ and about 70 per cent of relative humidity. At the beginning of the experiment, the eggs were scattered on the upper surface of the ricebran. The height of 20 grams of rice-bran in a container which was a paper box of (4×4)cm^2 in surface was about four cm at the beginning of the experiment, but it decreased with the progress of the larval development especially at high density of population. The rice-bran was divided into three layers of equal weight. In the experiment I, the counting of the number of individuals in each layer of the rice-bran was made at five days interval, and the width of their head capsules was measured to estimate their degree of development. On the other hand, in the experiment II, the population in each layer was reared separately, and the number of emerged moths was counted every day to estimate the number of individuals in each layer of the rice-bran at the time of its separation and the degree of their development at that time. Almost all of the larvae of young stage stay in the upper layer at both high or low densities. The movement of the larvae towards the middle and the bottom layers begins at the third instar and becomes frequent towards the final instar. The proportions of individuals at the middle and the bottom layer become high with increasing density, until the number of individuals in each layer becomes almost equal. The larvae in the lower layer are slightly more advanced in their degree of development than the larvae in the upper layer. The fully grown larvae move upwards, searching for a pupation site and pupate at the upper layer. Some of the individuals wander and pupate at the outside of the container when the density is high. It is concluded that the upward movement of fully grown larvae does not depend upon their density, while the downward movement of the young larvae and the escaping of the larvae of all stages from the container depend upon their density and occur only when the contact among the larvae is frequent. Some consideration were given comparing with the result of the author's preceding experiment (TAKAHASHI 1955), in which the larvae can emigrate from one vial to another.
Sargassum vegetation growing in the shallow sea around Ushibuka City, west Kyushu, Japan was surveyed in July, 1959. Eight survey stations were chosen (Fig. 1). At each station, the vertical range and coverage of each species of Sargassum were recorded from direct observations by skin diving. The lower limit of the range of Sargassum vegetation was recognized at about six m below the low water mark. The vertical range of a certain species was not the same among the stations, and the zonal arrangement of the species in relation to the depth was not obvious. The species belonging to the subgenus Eusargassum grow in the rather shallow sea exposed to moderate wave action. Sargassum patens grows predominantly in the shallow sea protected more or less from wave action. S. piluliferum and S. serratifolium were observed growing in deeper places under a wide range of wave action.