OF PERIPATUS CAPENSIS. 885 



Within the peritoneal investment comes a well-developed mus- 

 cular layer with a somewhat unusual arrangement of its layers, 

 there being an external circular layer and an internal layer 

 formed of isolated longitudinal bands. The epithelium is fairly 

 columnar, formed of granular cells with large nuclei, and is lined 

 by a prolongation of the external cuticle. It is raised into 

 numerous longitudinal folds, which are visible from the surface, 

 and give a very characteristic appearance to this part of the 

 alimentary tract. The muscular layers do not penetrate into 

 the epithelial folds, which are supported by a connective tissue 

 layer. 



NERVOUS SYSTEM. 



The central nervous system consists of a pair of supra-ceso- 

 phageal ganglia united in the middle line, and of a pair of 

 widely divaricated ventral cords, continuous in front with the 

 supra-cesophageal ganglia. 



It will be convenient in the first instance to deal with the 

 general anatomy of the nervous system and then with the 

 histology. 



Ventral Cords. The ventral cords at first sight appear to be 

 without ganglionic thickenings, but on more careful examina- 

 tion they are found to be enlarged at each pair of legs (PI. 48, 

 fig. 8). These enlargements may be regarded as imperfect 

 ganglia. There are, therefore, seventeen such pairs of ganglia 

 corresponding to the seventeen pairs of legs. There is in addi- 

 tion a ganglionic enlargement at the commencement of the 

 cesophageal commissures, where the nerves to the oral papillae 

 are given off (PI. 51, fig. 22 or. g.), and the region of junction 

 between the cesophageal commissures with the supra-cesophageal 

 ganglia, where another pair of nerves are given off to the jaws 

 (PI. 51, fig. 227 ri), may be regarded as the anterior ganglion of 

 the ventral cords. There are, therefore, according to the above 

 reckoning, nineteen pairs of ganglia connected with the ventral 

 cords. 



The ventral cords are placed each in the lateral compart- 

 ments of the body-cavity, immediately within the longitudinal 

 layer of muscles. 



