Abstract
There are many papers devoted to the inheritance of the egg-colour of silkworms by K. Toyama (1913), Y. Tanaka (1919, 1924, 1935), H. Uda (1923, 1924, 1932), E. Kawaguchi (1938 a, b), Y. Nakano (1931) and K. Suzuki (1936). In these reports we find two types of egg-colour, one being transmitted ordinarily and the other maternally. In my previous paper, I wrote on a maternal white-egg breed (w1) which seems to be analogous to w of Kawaguchi (1938 b) and wPR of Uda (1932). Fortunately I have had another white-egg breed (w2) which acts ordinarily. By crossing these two white breeds, I have come to the following conclusion.
1. The first white-egg breed may be represented as w1 W2PR and the second white breed as W1w2PR, where P and R are normal genes for p (pink eye) and r (red eye) respectively. W1 is assumed to be related to the production of hormonelike substance and its function exclusively takes place at the larval stage but not in the embryonic stage, hence maternal inheritance, while W2 produces immediately after fertilization the chromogen which gives rise to the normal egg-colour in the presence of the said hormone, hence ordinary inheritance. I support Kawaguchi's idea that the development of the egg-colour is a result of interaction of the hormone and the chromogen, I cannot, however, agree with him respecting to his conception of the pleiotropic function of these genes.
2. There is a linkage relation between w1 and w2, the crossing over value being calculated at 3.36% in the male, and O in the female.
