ONO, Yoshiaki and Tatsumi UEMATSU (Kagawa Univ., Taka matsu) Sequence of the mating activities in Oryzias latipes. Jap.J.Ecol. 18,1-10 (1968). The quantitative research on the chain reactions among the behaviour unit patterns recognized during development of the mating behaviour patterns was made as a preliminary step to study both the mechanism and meaning of the chain reactions in Oryzias latipes. One hundred and twenty one full-grown pairs of both sexes were observed. Each experimental material was isolated and feeded sufficiently for 72 hours before the experiment. Then a male and a female of the same body length were introduced simultaneously in the glass aquarium under the condition of controlled light in the dark room and their behaviour patterns observed for 30 minutes were recorded. No bait was given to them during the observation. The results obtained are as follows. 1) Fifty of the 121 pairs observed developed to copulation (M7) and spawning (M8). 2) From the quantitative research on the chain relation among the mating behaviour patterns the sequence of development of the mating behaviour is concluded to be as follows. Approaching (S1)→following (S2)→courting orientation (M1)→head-up I (M2)→courting round dance (M3)→head-up II (M4)→floating-up (M5)→crossing (M6)→copulation (M7)→spawning (M8)→ejaculation (M9)→fertilization (M10). 3) Considering both the degree of development of each mating behaviour pattern and the mean time from the beginning of the observation to the first occurrence of each behaviour pattern, the mating behaviour seems to develop along two following main processes. S2→M1→M3→M5→M6→M7-10 S2→M1→ M5→M6→M7-10 Regarding S_2→M1→M3 as phase I and S2→M1→M5→M6 as Phase II, the above mentioned processes are represented as follows. Phase I→latter part of phase II→copulation Phase II→copulation 4) Phase I has the biological significance of the promotion of the sexual drive of both sexes. 5) The female behaviour patterns, head-up I and II, are regarded as the avoiding behaviour due to insufficient sexual drive. These behaviour patterns result in the repeating of the male courting behaviour. Then the sexual drive of both sexes is promoted and the synchronization of copulation results. 6) There was observed the repeated phase I when the sexual drive of bath sexes was too low to copulate. Phase II occurred frequently when the sexual drive of the male is high, but that of the female is not so high. When the sexual drive of the male is low, the frequency of the occurrence of the mating behaviour is low or zero. In the pair prepared sufficiently to copulate, there are few repeated occurrences of both phases, or phase I is omitted.

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HOZUMI, Kazuo (Dept.Biol., Fac.Sci., Osaka City Univ., ) Kichiro SHINOZAKI (Sci.Educ.Inst., Osaka) and Yoshiya TADAKI (Gov.For.Exp.Sta., Tokyo) Studies on the frequency distribution of the weight of individual trees in a forest stand. I. A new approach toward the analysis of the distribution function and the -3/2th power distribution. Jap.J.Ecol. 18,10-20 (1968). A new method to analyse the frequency distribution of tree weight (w) in a forest stand was developed by introducing the three cumulative amounts, Y=[numerical formula], and M=Y/N. By this MNY-method, a new distribution density function, φ(w)=(√<B>/2A)w^<-3/2>, was derived for three stands of Abies, Betula and Cryptomeria. It is emphasized that this approach enables us to deal with biomass, density and other ecological quantities in absolute instead of relative scale, and to compare different stands directly with each other in terms of the parameters of the distribution function.

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TOKUI, Toshinobu (Hokkaido Salmon Hatchery. Fisheries Agency) and Satoshi INOUE (Institute of Applied Zoology, Faculty of Agriculture, Hokkaido University) On some inland waters in the Shiretoko Peninsula, northeastern Hokkaido, with particular emphasis on nature conservation. Jap.J.Ecol. 18,20-26 (1968). The present paper is a record of a limnological survey of Lake Rausu and two small rivers (Rusha and Teppanbetsu), situated on the Shiretoko Peninsula in northeastern Hokkaido. Lake Rausu and its surrounging area deserve strong future protection because their natural characteristics have been well preserved to date. It appears to us that the Rivers Rusha and Teppanbetsu are not worthy of nature conservation because of having been disturbed artificially.

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YASUDA, Toru (Fisheries Experiment Station of Fukui Prefecture, Tsuruga, Fukui) Studies on the fouling organisms in Nyuura bay, Fukui III. Observations on the ecology of a cirriped, Balanus amphitrite amphitrite DARWIN. Jap.J.Ecol., 18,27-32 (1968). Balanus amphitrite amphitrite DARWIN is a dominant species among acorn barnacles in Nyuura Bay and its vicinity, and one of the most harmful fouling animals in the area. During the period of observation from July 1965 to July 1966,the pelagic larvae of cirripeds, supposedly those of B.amphitrite amphitrite, occurred in the plankton samples taken from various spots in the bay, from late June to late December, during which the temperature at one meter depth varied from 10℃ to 28℃. The maximum occurrence of pelagic larvae was found from August to October (18℃ to 28℃ 1m). This suggests that the spawning season of this species continues from late June to late December with the maximum spawning in August-October. B.amphitrite amphitrite settled on suspended plates and gradually decreased in number from the head to the mouth of the bay, and the number was always largest at 1 m depth through the vertical range of 0-5 meters. Pelagic larvae of B.amphitrite amphitrite settled more abundantly on the plates colored dark such as black or red than on the plates colored light such as blue, green or white.

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SAISHU, Kozo (Seikai Regional Fisheries Research Laboratory, Nagasaki) Reproductive curve of the stock of Argyrosomus nibe, Kuroguchi, in the east china sea. Jap.J.Ecol. 18,32-39 (1968). An analysis was carried out concerning the variation of the stock of A.nibe by comparing the fluctuation of the spawner to that of recruitment size using the catch and effort statistics with size category. The amount of the recruitment was then correlated with the temperature distribution of the nursery ground during the spawning and early developmental period of the preceding year. 1. The amount of stock of the present species varied chiefly depending on the size of the recruitment. The fluctuation of the size then seemed to be influenced by (1) the abundance of the dominant brood stock occurring with an interval of three years, and (2) the dimensions of the suitable habitat within the nursery ground, which affects the size of the brood stock. The periodical occurrence of the dominant brood stock coincided with the age of the earliest maturation, i.e. three years old. As an index of the environment, an attempt was made to set the isothermal area of habitat, 23°〜24℃ for a narrow and 22〜25℃ for a wide range, using the mean surface temperature of the nursery ground during the spawning period of a particular population. 2. The relation between the deviation of the recruitment size from the mean of the annual fluctuation and the index of the environmental factor (the size of the suitable isothermal area in the present case) indicates that the maximum and the minimum values of recruitment size proportional with the variation of the isothermal area despite the fact that the mean values were always constant regardless of the change of the isothermal area. Thus, there appeared to be a natural adjustment in size affected by the density of the population.

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MIYAUTI, Tetuo (Laboratory of Takashima Pearl Farm Inc., Sasebo). Studies on the effect of shell cleaning in pearl culture-III. The influence of fouling organisms upon the oxygen consumption in the Japanese pearl oysters. Jap.J.Ecol. 18,40-45 (1968). In the Preceding papers, it was reported that the activity of shell movement, the amount of feces, the shell regeneration and the byssus secretion in the Japanese pearl oysters, Pteria (Pinctada) martensii (DUNKER) were decreased by the presence of fouling organisms. In order to clarify whether the work of shell cleaning is effective for increasing the growth of the bivalve and the quality of the pearl, the harmful influence of the presence of fouling organisms upon the oxygen consumption of the Japanese pearl oysters was studied in the present paper. Fouled pearl oysters were reared in three pearl farms in Sasebo Bay and their oxygen consumption before and after shell cleaning was measured. The apparatus employed was similar to Hall's experimental apparatus using the running water system. The results obtained are as follows : 1. The oxygen consumption in fouled pearl oysters changes by cleaning the shell; the rate of oxygen consumption in the cleaned pearl oysters amounted to nearly constant (0.07-0.10cc/g wet tissue/hour) for 14 days after shell cleaning. It seems that the rate of oxygen consumption was relatively slow in recovery. The recovery of the rate of oxygen consumption changes by the degree of the ill-effect of fouling organisms in fouled pearl oysters. 2. The rate of oxygen consumption in pearl oysters has close relation to the weight of the fouling organisms in fouled pearl oysters ; the greater the weight of fouling organisms is, the less the rate of oxygen consumption is liberated. 3. The degree of the ill-effect of fouling organisms upon the fouled pearl oysters varies with species of fouling organisms; the greater degree of the ill-effect of fouling organisms is seen with Balanus amphitrite communis DARWIN; and the less degree of the ill-effect is with Ciona intestinalis LINNE. The results mentioned above together with the outcome of the preceding paper suggests that the activity of the pearl oysters is harmfully influenced by the presence of fouling organisms, and the work of shell cleaning is effective for the production of pearls.

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