It was demonstrated in this series (XVII) that the brain innervates the secretion of the corpora allata (CA) through nerve commissures from the brain. As the sex-linked allelomorphic maturing genes (Lme < + L m < Lm) had been thought to control the function of the brain, the function of the brain by strains (genes) in the CA during the final 5th larval Instar was investigated. From experimental results, it was demonstrated that the recessive early maturing gene Lme, on the Z chromosome

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... the intermediate maturing gene + Lm, intermediately, and the dominant maturing gene Lm, weakly innervates the activity of the CA of the 5th Instar larvae. Materials and methods. The silkworms used in this experiment were larvae of four tetramolting crossings between J. 106 (+ V/ + V, Z "m/W) and T2 (+ v/+ V, Z L m/ZLme), between J. 106 and Di (+ v/+ V, Z "m/Z +Lm), between J.106 and Kp (+ V / + V, Z L m/Z Lm), between E. 606 (V'/V', ZLm/W) and c (V3/V3, ZLme/ZLme) and larvae of reciprocal crossings between T2 and Kp. Their eggs were incubated at 25°C in the light. Operating methods for the extirpation of the CA or the transplantation of the brain-corpora allata (Br-CA) complex or the CA were the same as the one previously reported (Report XVII). This experiment was ascertained by repeating two times. Results. 1. Function of the Br-CA and the CA during 4th and 5th larval instar. The activity of the Br-CA and the CA during the 4th larval instar was stronger, especially in the late half instar as compared with that of the Br-CA and the CA during the 5th larval Instar as shown in Figs. 1 and 3 . The secretion of the CA during the 4th instar continued until the 4th molting, but during the 5th instar it decreased with age and ceased at the middle stage of the same instar. The Br-CA always showed stronger activity than the CA. According to thin-layer chromatography (Report XIX), ecdy-