外山亀太郎と明治期の蚕糸業における蚕の「種類改良」

抄録

In 1891, Silk Association of America warned Japanese vice-consul in New-York that the quality of Japanese raw silk was sub-standard. It advised both an improvement of silkworm breeds and a reduction in Japan's more than 300 silkworm breeds. In 1893, the engineers at the Institute of the Ministry of Agriculture and Trade (I.M.A.T.) began applying themselves to the task, though there was little scientific knowledge of breeding by crossing. By 1910, I.M.A.T. could not develop suitable silkworm breeds. However silkworm breeders had achieved some improvements through hybridization. When Kametaro Toyama who had known the breeder's breeding by crossing, began to interbreed in 1900, he did not know Mendelism. But Toyama had learned about the heredity and variation of hybridization, through the book, 'The Germ-Plasm' of A. Weismann. In 1901, he read the paper of H. de Vries and found out about Mendelism. From 1902 to 1905, he continued silkworm cross-experiments in Thailand (then Siam). In 1906, he confirmed that Mendel's law could be applied to silkworm in his doctoral dissertation. And he insisted on making f_1 hybrid for improvement of silkworm. In 1909, he published the book, 'Sansyuron' which he presented his method of breeding based on Mendelism. Only in 1910 did the engineers at the I.M.A.T., including S. Ishiwata, accept Mendelism and Toyama's methodology. After that, under the leadership of Toyama, I.M.A.T. began improving silkworm breeds and succeeded in producing an excellent f_1 hybrid by 1913. As a result, the Japanese raw silk was rapidly improved in quality.