SOME ASPECTS OF THE STRUCTURE OF THE NERVOUS SYSTEM IN THE ANEMONECALLIACTIS

Abstract

In the light of existing work on tbe behavioral physiology of this anemone, the structure of parts of the neuroimiscular system has been examined in detail. In the sphincter region, the morphological basis for rapid through-conduction and motor innervation is a network of bipolar nerve cells, which is connected to the similar retractor nerve-nets of mesenteries. Sphincter muscle fibers are arranged at the periphery of tubes, which form a meshwork within the mesogloea. Bipolar nerve cells appear to run in these tubes. Neurites also reach the sphincter from the endodermal nerve-net by penetrating the mesogloea directly. The nerve-net over the circular muscle is richer than in other parts of the column, but shows similar features. It includes small multipolar cells of unknown function. Coordination between different parts of the anemone is discussed in terms of possible pathways for the transmission of excitation. For example, bundles of retractor and parietobasilar muscle fibers continue from both surfaces of mesenteries into the mesogloea of the pedal disk, suggesting a possible route for neurites passing to or from the ectoderm. If confirmed, the existence of this route could throw light on a number of sequences of behavior.