Initial report of this trematode was made by Hasegawa (1927) who found the metacercaria from the fins and scales of trout, Plecoglossus altivelis and also its adult worm from the intestine of a fish, Parasilurus asotus. Subsequently Takahashi (1929) reported its first intermediate snail host, Semisulcospira libertina, with a description of its cercaria and metacercaria. In 1935 Hasegawa again described the metacercaria and its adult worm under the name Exorchis major. Yamaguti (1938) set up a new genus Pseudexorchis for this species and separated from the Exorchis in two fundamental reasons; the extent of intestine and the position of genital organs.
It is important to distinguish this cercaria from the others, especially from that of pathogenic famous Metagonimus parasitic in the same snail host, because of the strong resemblance of structures between them. As to the second intermediate host, as many as about twenty species of fresh water fishes has been reported by Okabe (1940), Date (1943), Miyoshi (1948), Takahashi (1953), etc. Therefore it seems also important to distinguish this metacercaria from that of pathogenic Metagonimus, Clonorchis, etc., as these cysts afire generally found in various fishes side by side with that of Pseudexorchis major.
The author had opportunities of getting this cercaria from the snails at several areas in Japan, and also the metacercariae from the fins of experimentally infected gold fish, Carassius carassius. The following is a more detailed redescription of this cercaria, especially on its excretory system, sensory hairs and oral spines, and also the redescription of this metacercaria, especially on its development.

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The nucleus enumeration method for the growth estimation of tissue-cultured cells was devised and fully examined for its preciseness in practical use by Sanford, Earle et al. (1951) . Katsuta et al. (1954) applied the method with a simplification. The change in cell population can be exactly pursued by this method.
Using the nucleus enumeration on the basis of the same principle as the original authors with some modifications, the present authors have analysed the growth mode of the HeLa strain cells. The cells originally obtained by Gey et al. (1952) from an epidermoid carcinoma of the cervix have been maintained in our laboratory through more than 60 culture passages without any appreciable changes in biological characters.
In the present paper, the detail of the growth estimating procedure will be described and some factors of variances in the process considered to influence the results will be discussed.

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As a result of the improvements of tissue culture techniques, it has recently become possible to clarify the growth mode of animal tissue cells more exactly than formerly. Earle and his colleagues, in their studies concerning the L strain of mouse fibroblasts, devised a procedure for preparation of replicate tissue cultures (Evans, Earle et al., 1951) and a growth estimating method based on nucleus enumeration (Sanford, Earle et al., 1951), by which they pursued cell proliferation in vitro using the increase in the number of cells as a scale. They proved that an inoculum size larger than a certain level of cell number was necessary for the L strain cells to grow therein and that the cells implanted in a proper number grew rapidly to reach a maximum and then declined (Earle, Sanford et al., 1951) . They reported later that a “lag or adaptation interval” existed in “fluid suspension” cultures within the first 24 hours (Earle, Schilling et al., 1954) . Katsuta et al. (1954) and Graham et al. (1955) observed the cell growth in tissue culture, using different cell types and different culture methods. A survey of these data gives one the conception that cells cultivated in vitro proliferate displaying some growth phases comparable to those of bacteria.
The present authors have been studying on the growth characteristics of the HeLa strain cells in stationary cultures. The existence of a logarithmic phase in the course of their growth was confirmed. The growth estimating procedure based on nucleus enumeration and its accuracy were discussed in detail in the previous report by Takano, Yamada and Yaginuma (1956) . In the present paper, the whole course of the growth curve of the HeLa cells is analysed, which is eventually divided into the three stages of lag, logarithmic, and stationary phases.

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Among several methods for the growth estimation of tissue cells cultivated in vitro, the measurement of areal growth of cell colonies has been most generally used. Ehrmann and Gey (1953) improved the procedure of areal measurement so that the indirect method became considerably reliable. Sanford et al. (1951) devised a more precise quantitative method of enumeration of cell nuclei on the basis of a procedure of preparing replicate cultures (Evans et al., 1951) .
The HeLa strain cells used in our experiments grow on the glass wall forming colonies of almost monolayer even if they are implanted as a homogeneous suspension of single cells. Besides the colonies can be readily disintegrated into single cells by the treatment with trypsin or citric acid. Therefore, both measuring techniques mentioned above are applicable to the cells.
In the present paper, some methodological considerations in the practical use of both techniques and the correlation between colonial area and cell population are discussed using the HeLa strain cells as the object.

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While considerable work has been done on Clostridium botulinum, both type A and type B, comparatively little is known of the other types, especially of type E. This is due to the infrequency of cases and to the small number of isolated strains of this type.
Clostridium botulinum type E was first isolated in Russia from the intestines of a sturgeon and was identified as such in U.S.A. by Ounnison, Cummings and Meyer (1936) . Since then, at least 18 outbreaks of type E botulism have emerged up to 1955 (Dolman and Chang, 1953; Nakamura et al., 1954) . Eight instances occurred in North America: 4 in British Columbia, 2 in New York State, one in California, and one in Alaska. One instance was reported from Russia and from Denmark respectively. In Japan, twelve outbreaks have so far occurred, nine of them taking place in Hokkaido.
As pointed out repeatedly by Dolman and his co-workers (1950), one of the most important vehicles of type E botulism is fish. This view is also supported by the fact that all the twelve outbreaks encountered in Japan have proved to have been caused by “Izushi” made of raw fish.
The particularly high rate of occurrence in Hokkaido would, therefore, be due to the custom of the inhabitants of eating uncooked fish foodstuffs and also to a possible wide-spread dissemination of type E spores in this province as was detected by the present authors.
Strange to relate, in Japan, no cases of botulism have been reported in the literature up to 1952. It is also curious that indigenous spores of Clostridium botulinum have been believed for so many years to be absent from the soil of this country.
In previous papers (Nakamura et al., 1952; Nakamura et al., 1954), however, the present authors reported several outbreaks of type E botulism encountered in Hokkaido. They reported at the same time the isolation of several strains of type E organisms, both from the foodstuffs involved and from samples of soil collected in this province.
This paper summarizes the epidemiology of the type E botulism observed in Hokkaido and the bacteriological examinations of the type E strains isolated by the present authors.

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Excepting a single record of Simulium oshimanum Shiraki, which was described in 1935 from Amami-oshima Is., the simuliid fauna of the Ryukyu Islands has not been investigated at all.
In this paper, the author reports four additional species, S. (Nevermannia) batoense, S. (N.) aureohirtum, S. (Sirnulium) japonicum and S. (S.) tuberosum, which were collected by Dr. T. Shiraki, Dr. M. Sasa, Messrs. K. Sato and H. Tanaka during the years from 1953 to 1955, and now preserved in author's collection.
One of the four species, S. batoense is new to the fauna of Japan, and a redescription of this species is presented together with a description of the male insect of S. japonicum which has not been published yet.
It will be of interest from the faunal point of view to note that S. batoense and S. aureohirtum, which have been originally known from the Oriental tropics, occur in the Ryukyu Islands together with S. japonicum and S. tuberosum, which commonly occur in the Palaearctic area.

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Broadly speaking, the type of Salmonella infections is either a gastroenteric or a typhoidal and septicemic disease. In rare instances the food-poisoning phase progresses on to the gastroenteric and eventually to the typhoidal or septicemic type of the disease. In men, a few species, such as S. typhi, S. paratyphi A, B and C give rise to a disease characterized by a fairly long incubation period and the predominance of septicemic, over intestinal symptoms. The great majority of the Salmonella species, however, produce gastroenteritis of the food-poisoning type in children and adults, or acute enteritis in infants characterized by a short incubation period and the predominance of intestinal, over septicemic symptoms.
In typhoid type of infection, Salmonella organisms invade through the intestinal wall of host, multiplying mainly in lymphoid tissues and resulting in bacteremia, while in gastroenteric type microorganisms normally do not cause general infection and the lesions are confined mainly to the intestine (Elkeles and Standfuss, 1931; Tulboch, 1939; Kojima and Hatta, 1942; Kuwahata, 1942; Kuwahata, 1943; Sutherland and Berger, 1944; Wilson and Miles, 1946; Edwards and Bruner, 1948; Uetake et al., 1948) .
Though the above is a generally well-known fact, it has not been made clear as yet wherefrom the difference of infection type arises. It is also clear that infection generally depends upon the relationship between hosts and infecting agents; for example, S. typhi produces typhoid infection in man but not in other animals, while S. enteritidis is capable of producing infection in mice, but not in man.
However, when the host is restricted to a certain species, for example, to human beings, it seems reasonable to postulate that some difference may exist between infectious agents of different types of infection. On the other hand, recent advances in biochemistry have made clear that almost every type of life phenomenon is closely related with metabolism; for instance, muscle contraction depends upon phosphate metabolism (Engelhardt, 1946), and respiration and fermentation depend upon biological oxidation and reduction (Lardy, 1949; Stumpf, 1954) . Hence it seems possible that the types of bacterial infection may depend on the metabolism of bacteria and host animals. This has led the authors to the comparison of physiology of Salmonella species.
The outline of a part of the research along this line was reported in brief note (Uetake and Makino, 1954), and this paper will deal with a more detailed description.

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