Abstract
1. From the original tumor strain, or bw tu, a strain having only the tumor gene, or tu (53 d), was isolated. Various eye-colour strains were mated with tu (53d). From the offspring of these matings the following tumor strains were newly estabiished: bw tu, v tu, cn tu, v bw tu, tu st, and bw tu st. The incidence of tumor in each strain was studied.
2. The results show that the incidence of tumor increases when the tumor gene is accompanied by the eye-colour gene. According to the rate of increase in the incidence of tumor, newly established strains are arranged in a line as follows: tu, bw tu, v tu, cn tu, v bw tu, tu st, and bw tu st.
3. Eye-colours of these eye-colour mutants are considered to be regulated by the tryptophane metabolism in the development of Drosophila. It is, therefore, assumed that the incidence of tumor has a certain close connection with the tryptophane metabolic system.
