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Genetic and molecular investigations were carried out with 10 Japanese Drosophila melanogaster strains on P-M system of hybrid dysgenesis. The strains used here were collected in the years from 1952 to 1984 from various natural populations, and have been maintained in our laboratory. The whole genomic Southern hybridization was performed by using the 2.9-kb P element and the internal fragments as probes. Five strains possessed no P element copy and the other 5 strains possessed mainly incomplete P elements which had internal deletions. The former 5 strains were M, 2 of the latter were Q, and the remaining 3 were M' strains. Hikone-R, collected in 1952, had no P element copy, while Hikone-H, collected in 1957, was the earliest observed to possess multicopies of an incomplete P element. This revealed that P elements in Drosophila melanogaster were present more than 30 years ago in Japan, as already shown to have been the case on the American continent.

Inheritance of resistance to insecticides in Drosophila has been studied by many workers (Tsukamoto and Ogaki 1953, 1954 ; Ogaki and Tsukamoto 1953 ;Bochnig 1954; Oshima 1954 Oshima , 1961 Oshima and Hiroyoshi 1956 ; King 1954 King , 1955Crow 1954Crow , 1957 Tsukamoto 1955 ; Tsukamoto and Hiroyoshi 1956 ; Tsukamoto, Ogaki and Kikkawa 1957; Ogita 1958 Ogita , 1961 Merrell 1960; Kikkawa 1961 Kikkawa , 1964, and radioresistance has been studied by Ogaki and Nakashima-Tanaka (1966). In Drosophila nelanogaster the resistance to DDT, BHC, parathion and sevin, and the sensitivity to phenylthiourea are mainly due to a second chromosomal gene located around 64-66.Then the resistance to nicotine sulfate and phenylurea is mainly due to a third chromosomal gene located around 49-50.In the present paper the authors are dealing with the genetical analysis of resistance to ether anesthesia.The inheritance of resistance to ether has not been established as far as we are aware. Rasmuson (1955), however, studied on the inheritance of ether sensitivity in Drosophila melanogaster. He found that an outstanding sensitivity to anesthesia in Drosophila seems to depend on cytoplasmic factors as well as chromosomal genes.He stated that the sensitivity to ether was transmitted by the sperm of sensitive strain, but a reactive system was present in the cytoplasm of the egg, and the sensitivity occurred under an interaction between genes and cytoplasm.Some preliminary accounts may be found in our previous report (1967). MATERIALS AND METHODSIn August, 1961, one ether resistant female fly appeared from Mino-H wild strain in our laboratory.The progenitors of Mino-H strain were collected from Mino City in 1957. After successive selections by deep anesthesia two lines of resistant strains from the same origin were ready for our experiments.We call them Eth strains (ether resistant strains), and Eth-13 strain indicates the strain which was obtained by the selection for 13 generations, and Eth-28 strain was procured by the selection for 28 generations successively, and the phenotype of these ether resistant strains shows yellowish body color finally.The flies used for the experiments were cultured on a following larval medium (15 % crude sugar, 2 % dry yeast, 5 % rice-bran and 2 % agar in water).The culture of flies and all the experiments were undertaken at 25°C + 0.25, and 40-60 per cent relative 1) Research student from the School of Medicine, Kobe University.

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The effects of chloroform on three strains (Eth, Quick Sand, and bw; st; svn) were investigated genetically. Adult flies at 24 hours of age were anesthetized with chloroform for 0.5 and 1.0 minute, and mortalities were assessed 4 days later. The Eth strain was resistant and the Quick Sand and the bw; st; svn strains, susceptible to the chloroform. Reciprocal crosses between the Eth and the bw; st; svn strains showed that the resistance to chloroform was completely dominant over sensitivity and that maternal or cytoplasmic effects were negligible. A major gene (s) with respect to chloroform resistance is located on the X-chromosome, and a minor gene(s), on the second chromosome. We reported that the Eth strain was more resistant to ether than the Quick Sand and the bw; st; svn strains. Thus, it can be said that a cross-resistance to ether and chloroform is found in the Eth strain. The resistance to ether, as well as to chloroform, is a completely dominant trait with no maternal or cytoplasmic factors. However, the locus of the major gene(s) for the ether resistance is 61± on the third chromosome, and the minor genes are on both the X-and the fourth chromosomes. Therefore, resistances to ether and to chloroform are controlled by different genes. This suggests that the mechanisms of resistance to ether and to chloroform are different.