Some connections of optic lobes with supraesophageal ganglion of the dragonfly Aeschna grandis

Abstract

Optic centers of insects were the object whose study provided A.A. Zavarzin with the idea of par� allelism of histological structures. In Zavarzin’s point of view, the nervous apparatus of vision or� gans of the dragonfly of the genus Aeschna can be ascribed to the part of the nervous system that cephalizes the trunkate brain and the visceral ner� vous system [1]. Zavarzin studied neuronal relations of all three optic ganglia of each animal side [2, 3]. Connec� tions of these structures between each other have remained unstudied. The last instar larvae of the dragonfly Aeschna grandis, before alating, were injected with a syringe with 0.06% methylene blue in 0.75% NaCl through the extremity of the second leg pair. To prevent leak of the methylene blue solution, a ligature was placed on the leg. After 1 h the animals were dis� sected, the CNS was rapidly removed and fixed in 16% ammonium molybdate for 16 h. The material was washed out, dehydrated with absolute ethanol, and cleared in xylene. The total preparations were