Abstract
Fifth-instar silkworm larvae just after ecdysis were inoculated with either hexagonal or tetragonal cytoplasmic polyhedron virus. Some of the inoculated larvae died during the larval stage, but some emerged as adults. They were crossed between each other. When the larvae hatching from the eggs which were obtained from these crosses reached the fifth instar, cold treatment was carried out on them to induce the development of cytoplasmic polyhedrosis. When larvae died after the cold treatment, they were examined microscopically. The proportion of the number of larvae containing tetragonal cytoplasmic polyhedra in the midgut as compared to the number dead from cytoplasmic polyhedrosis was higher in the progeny of silkworms which were inoculated with tetragonal polyhedron virus than in the progeny of silkworms which were inoculated with hexagonal polyhedron virus. The author is inclined to postulate that normal silkworms transmit the cytoplasmic polyhedrosis virus of the hexagonal type to the next generation in an occult state through the germ cell and that when normal larvae were inoculated with the tetragonal polyhedron virus, some of the larvae transmit the tetragonal polyhedron virus to a part of the next generation in an occult state.
