The first extensive ecological study on Oncoinelania nosophora was made by Sugiura (1933) . He succeeded in rearing the snail by utilizing earthenware flower pots, and demonstrated that it is oviparous, laying its eggs separately and then covering each one with a layer of soil. He also observed the hatching of the egg and the development of the young snails to the adult stage.
More recently, McMullen et al. (1951), Tsuda (1952-53), Kawamoto (1952-54), Okabe and co-workers (1952-59), Komiya and co-workers (1957-59), and Mori and co-workers (1952-59), have reported on the ecology and physiology of this snail. The following is a summary of the observations that have been made by these workers.

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Pathogenic behavior of Escherichia coli has been explored with regard to necrotizing power, hemolysis, toxicity for mice, and other characteristics. On the other hand, the presence of certain pathogenic Escherichia culture has been clarified by serological investigation. However, when a culture of Escherichia coli, the sero-type of which is different from that of any known pathogenic organism, is isolated from gastro-enteritis, it is very difficult to determine whether the culture is the causative agent of the disease or not.
Sjöstedt (1946) found that Escherichia cultures belonging to certain 0 groups (2, 4, and 6) were frequently hemolytic, confirming Ewertsen's finding (1946) that hemolysis and the capacity of producing necrosis were related to each other.
Recently, De and Chatterje (1953) performed rabbit loop experiments to study the action of Vibrio cholerae on the intestine. De, Bhattacharya and Sarker (1956) extended the experiments to determine the pathogenicity of Escherichia cultures isolated from acute and chronic enteritis. From the results of their experiments, they suggested that the serological properties of the cultures might not be correlated with their pathogenicity for the rabbit intestine.
The authors (Namioka, Urushido and Sakazaki, 1958) carried out an experiment similar to that of De et al. using about 40 cultures isolated from transmissible gastroenteritis in pigs caused by a viral agent, and concluded that, in this case, toxic Escherichia organisms, which might have normally been harbored in the large intestine, migrated into the small intestine where they aggravated enteritis in association with the causative agent. Moreover, so far as Escherichia organisms isolated from transmissible gastroenteritis are concerned, no remarkable relationships were observed among 0 inagglutinability, hemolytic and necrotizing powers, and pathogenicity for the rabbit intestine.
Rolle and his co-workers (Rolle and Kalich, 1955; Botze, 1956) described that various toxic strains of Escherichia possessed an ability of agglutinating the sperm of the dog, while atoxic (non-pathogenic) organisms were lacking in such an ability.
Many attempts have been made, however, to differentiate the culture of pathogenic Escherichia organisms from that of non-pathogenic.
It would be very difficult to distinguish one from the other with any known procedure, although differentiation was possible among various types of disease caused by these organisms in man and animals.
It is well known that by using some reagents the invasiveness of certain organisms is enhanced directly or indirectly and, consequently, the virulence of the organisms seems to be intensified. Nungester et al. (1936) reported that Salmonella typhosa and some other organisms, when treated with mucin, increased their virulence. Such enhancement of pathogenicity was also demonstrated with the spreading factors discovered by Duran-Reynals (1942) . Chain (1939, 1940) described that the diffusibility of the organisms into certain tissue was accelerated when the host was administered with hyaluronidase. This effect is presumed to be due to an increase in tissue permeability which results from the enzymatic hydrolysis of hyaluronic acid and with facilitates infiltration and spread of pathogenes.
Recently, an assumption has been made on the possible presence of a wetting agent, a kind of surface activate agent, by the function of which the surface tension of tissue cells is depressed and capillary permeability increased. Consequently, this agent might facilitate the access of organisms to the tissues of their hosts. Christovao (1957) descovered that the pathogenicity of Shigella dysenteriae and Sh. flexneri for mice was consistently increased as shown by their LD₅₀ 100 to 2, 000 times as small as those of the controls.

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Coe virus has drawn some attention since the first report of this virus by Lennette et al. (1958) . This virus seems to be of some importance especially at military recruit stations, because the successful isolations of this virus reported so far were all achieved among military recruits (Lennette et al., 1958; Pereira and Perira, 1959; Van der Veen et al., 1960) . During the course of our studies on an epidemic of adenovirus type 7 infections in Katsuta Self Defense Forces Camp in Ibaragi Prefecture, a virus was recovered from a civilian working at the camp who suffered from mild upper respiratory illness. The virus was later found to be serologically identical with the prototype strain of Coe virus given us kindly by Dr. E. H. Lennette. The present publication will deal with description of the patient yielding Coe virus and also some serological surveys of the Coe virus antibody carried out in various populations in Japan.

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It was more than 20 years ago that Breedis et al. (1938) and Mider et al. (1939) reported on the effect of freezing on some transplantable mammalian tumors and the normal skin. Since then many investigations have been made to preserve mammalian tumor cells at a low temperature by Snell et al. (1949), Craigie (1949), Blumenthal et al. (1950), and Warner et al. (1950) . Especially mouse leukemic cells (Gabrielson et al., 1952) and ascites tumor cells (Morgan et al., 1956) made themselves suitable materials to searching for the optimal conditions for storage of animal tumor cells. Recently several mammalian cell lines cultivated in vitro have also been stored successfully for a long term by workers in the fields of tissue culture, virology, cell biology and so on such as Scherer and his colleagues (1954, 1960), Westwood et al. (1957), Swim et al. (1958), van der Veen et al. (1958), Hauschka et al. (1959), Stulberg et al. (1959), and Craven (1960) . The longest case so far reported was of HeLa and L strains (Scherer, 1960) which proved to be viable after 4 to 5 years' storage. In almost all cases, the important condition for successful storage seemed to be the concentration of glycerol mixed with serum or growth medium containing serum as well as the temperature for keeping cells. The optimal concentration of glycerol for many types of cells was revealed to be 5 to 20%, and the temperature to be around -70°C, ranging from -60°C to -80°C.
For the purpose of maintaining cell lines including altered sublines without further changes to give feasible materials to the study on variability of mammalian cells in vitro, several experimental series have been made in this laboratory. The present paper deals with the storage of 15 mammalian cell strains (13 human, a rat and a mouse cell line) . Among them was the strain HeLa which could be kept viable as long as 19 months, showing the capacity of multiplication after thawing. The other lines of the human, rat or mouse origin showed viability and multiplicability after 5 to 12 months' storage. For the strain L derived from the mouse and JTC-6 from the rat, the optimal concentration of glycerol was proved to be less than that for human cell lines.

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The infection experiment of Paragonimus westermani in its first intermediate host, Semisulcospira libertina, was made by Nakagawa (1915), Kobayashi (1918), Yokogawa (1919) and Miyairi (1919, 1934) . But due to the difficulty in rearing this snail for a sufficient time after infection, no cercaria thereof was obtained in these experiments.
The present authors succeeded in maintaining this snail for a long time after exposure to miracidia, rendering possible the experimental infection of it with the miracidia of Paragonimus westermani, and were able to obtain the cercariae of this worm. The following is the summary of the results.

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