NO. 4 NERVOUS SYSTEM OF A CENTIPEDE — LORENZO 23 



The neural lamella stains bright pink with picrofuchsin. There are 

 no cells present in this homogeneous sheath. In sections which are 

 distorted it is seen to consist of several laminae. The cells in the 

 underlying layer are thought to produce the neural lamella. 



The cells of the perilemma are differentiated in silver and cresyl 

 violet preparations. At least three nuclear types are distinguishable 

 on the basis of shape and staining properties (pi. 5, fig. i). One type 

 (a) of nucleus is almost spherical. It is almost opaque and the cell 

 has very little cytoplasm. A second type (c) has an oval nucleus 

 whose chromatin stains a bluish black and is heavily distributed 

 throughout the nucleus. A third type (&) stains light pink. Its chro- 

 matin is aggregated along the nuclear membrane. A clump of chro- 

 matin, probably a nucleolus, is eccentrically placed against the nuclear 

 membrane. The third type resembles one of the neuroglial cells which 

 occur within the cortex and neuropile in that it stains pink and has 

 similarly distributed chromatin. The cell types found in hipuncticeps 

 are similar to those described in the thoracic ganglion of Periplaneta 

 (Hess, 1958). 



The neuroglial nuclei are smaller than those of the neurons and 

 stain less intensely. Two types of ''glial" cells can be differentiated on 

 the basis of their nuclear properties. Both nuclei are ellipsoidal 

 (3X5 micra) but occasionally assume different shapes, which may be 

 the effect of fixation or position in the ganglia. They are generally 

 kidney shaped in the neuropile. Dark and light staining cells are 

 present in silver and cresyl violet preparations. The dark cells have 

 a great abundance of chromatin which is distributed in clumps and 

 strands throughout the nucleus and which stains black. The light 

 cells have less chromatin. This is aggregated near the nuclear mem- 

 brane and stains pink. Eccentric nucleoli less than a micron in diam- 

 eter are present. The two types of glial cells are represented in plate 

 5, figure 2. 



2 Cellular cortex. — The brain of hipuncticeps consists of an outer 

 cellular cortex and an inner fibrous core. The cortex contains the cell 

 bodies of the neural elements, and the fibrous core, also called the 

 neuropile, neurospongium, or, by some European authors, "punkt- 

 substanz," contains the cell processes or nerve fibers. Routine histo- 

 logical stains, such as haematoxylin and eosin, trichrome stains, etc., 

 do not reveal the precise fibrous nature of the neuropile ; special silver- 

 staining techniques are required. The cortex and neuropile exhibit a 

 precise bilateral symmetry. Even the number and location of the 

 nuclei reflect this symmetry. 



Sensory neurons have not been demonstrated in the ganglia of 



