Abstract
The natural mutant character, Dirty marking (Di), of the silkworm, Bombyx mori, which has been discovered by Prof. Tanaka in 1939, but not reported about it, is characterized by dark dorsal skin covered by numerous dark spots and lines, just like the intermed ate between the normal and moricaud markings. This character is inherited as dominat, but as recessive for the semi-lunar crescents and star spots to the normal.
From the results of crossing between some marking strains, plain (p), normal (p+), striped (pS), multi-star (ms) and dirty (Di), it is postulated that most strains of the silkworn have generally a gene which forms the special tissue limitted to the places of the semi-lunar crescents and star spots in the larval skin. The author calls it the “Fundamental Crescent” gene.
This gene determines primarily the places of the crescents and stars and forms the special tissue which enables the formation of pigments, p+ gene produces pigments secondarily in that special tissue. If no pigment formation takes place, the character results in the plain marking. The multi-star has only a gene which modifies the action of the fundamental crescent gene, but has no pingment forming action. The striped gene does, however, not interact with the fundamental crescent gene at all.
