Four kinds of cytoplasmic inclusions can be recognized in the neurones of Leander serratus and Astacus fluviatilis. These are (i) spherical or almost spherical bodies, which often show a differentiated cortex and medulla; (ii) mitochondria, in the form of minute granules and short rods; (iii) Nissl substance, uniformly dispersed; (iv) ‘trophospongial’ structures, which are connected with the surface of the cell, and ramify in the form of delicate filaments throughout the cytoplasm.

Neutral red colours the spherical bodies in life; it does not seem to interfere with their optically visible structure. The spherical bodies often burst open into rods and crescents; these correspond to what other authors have called ‘Golgi apparatus’ or ‘dictyosomes’. The term ‘Golgi apparatus’ has also been applied by certain authors to the ‘trophospongial’ structures.

Histochemical study reveals that the surfaces of the spherical bodies, which are blackened by osmium tetroxide or silver nitrate in the Golgi methods, respond to tests for phospholipid after an ‘unmasking’ fixative has been used. The evidence also suggests the presence of cerebroside (galactolipid) in these bodies.

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