THE RELATION BETWEEN NEUROSECRETION AND CELL DIFFERENTIATION IN THE OVOTESTIS OF SLUGS (GASTEROPODA: PULMONATA)

Abstract

Cytodifferentiation in the germinal epithelium of the ovotestis of slugs is approached experimentally. The tentacles of the slugs were cut off and the animals maintained for different lengths of time before the ovotestis was examined. In both species of slug used, Arion subfuscus and Arion ater, the experimental animals showed a noticeable increase in the number of eggs, when compared with the control. Solutions of brain homogenate and tentacle homogenate were then injected separately into intact animals. The brain solution apparently stimulated the production of eggs, the numbers being nearly equal to that produced by cutting the tentacles. The tentacle solution injected into the animals produced no increase in the number of eggs, and in young animals the normal growth of the ovotestis was inhibited. Cytological study of the brain and tentacles reveals neurosecretory cells and a close association with the blood system of the animal, suggesting a basis for a hormonal system. In this case, a theoretical concept of a dual hormonal control is put forward, to explain the production of male cells first by the tentacle hormone, followed by egg production under the control of a brain hormone.