108 F. H. STEWART. 



The nervous system consists of the circumoesophageal 

 ring and ganglionic collar and of the ganglion in the wall of 

 the rectum or cloaca. These are the only structures which 

 are iti any way separated from the general epidermis. 



The nerve-ring (PI. 1 , fig. 4, nr) lies at the iunctiou of the 

 first and second thirds of the oesophagus, and consists of fine 

 fibrillse united into a bundle. It contains a few nuclei, 4 to 6, 

 which resemble those of the Type 1 cells of the epiderm, but 

 are somewhat smaller. A sheath of fine connective tissue 

 derived from the fibrillar stroma which here fills the space 

 between the body-wall and the gut encloses the ring. The 

 sheath stains more deeply than the nerve-fibrils. Processes 

 which in places can be shown to be hollow pass off from the 

 sheath, and join the connective tissue surrounding the cells of 

 the collar and the muscle-cells. I have in a few instances 

 found nerve-fibrils in these hollow processes, but they are so 

 fine that it is not possible to follow them for any distance. 

 They pi'obably connect the ring with the collar-cells and 

 the longitudinal lines. 



The circumoesophageal collar (PI. 1 , figs. 1 and 3) extends 

 from nearly the commencement of the oesophagus to a short 

 distance behind the nerve-ring, and is composed of cells grow- 

 ing in from the longitudinal lines. It completely fills the space 

 between the body-wall and oesophagus. In preparations of 

 the entire animal it can be clearly seen as a compact cylinder 

 of cells. 



The cells are of three types, viz. cells of the same character 

 as 'I'ypes 1 Jvnd 2 of the longitudinal lines, and in addition 

 large oval cells (PI. 7, fig. 3, 6c i) "016 mm. in diameter, with 

 abundant protoplasm which may show very faint, irregular, 

 basophile markings, the nucleus "OOGl mm. with a definite 

 nuclear membrane, finely granular acidophil contents, the 

 chromatin aggregated into a large spherical pseudo nucleolus. 

 These cells are, I believe, identical with the basophil cells 

 which occur in the space between the body-wall and the gut in 

 other regions of the body; they differ from them, hoAvever, 

 in some points, and as I can only speculate in regard to their 



