NOTES ON SYNAPTA. 239 



The body walls conform to the typical structure (PI. 

 XVI., figs. 1 and 2). Beneath the ectoderm (ect) is a 

 thick layer of connective tissue (ctl). Then comes the 

 layer of circular muscular fibres {cm) lined by the ciliated 

 epithelium of the body cavity. 



The bodies to which I have twice referred under the 

 name of miliary granules are ectodermal structures which 

 project wart-like above the general surface of the body 

 (PL XVI., figs. 1 and 2, mt). In the substance of each 

 is lodged a relatively large ganglion-like mass of nerve 

 tissue (PL XVII., fig. 7). From the latter a large number 

 of fibrillar processes radiate, some if not all of which 

 become continuous with the filiform basal ends of the 

 ectoderm cells, the " sense cells" of Hamann and other 

 writers. Many of the ganglion-like masses are continuous 

 with bundles of nerve fibres which most probably arise 

 from the radial nerves. Another point of interest is the 

 presence in the connective tissue layer of what for want 

 of a better name, I have called giant cells, in allusion to 

 their large size. Occasionally they occur in groups of two 

 or three, but as a rule singly (PL XVII., fig. 8). The 

 protoplasm is finely granular, and the majority of the 

 cells are multinuclear, the larger ones invariably so. They 

 seem to occur only in the most superficial portion of the 

 connective tissue layer, just beneath the ectoderm. 



The nervous system consists of a circum-oral ring 

 (PL XVI., fig. 1, conr) from which five radial nerves (m) 

 proceed along the radii of the body. A well marked sheet 

 of nerve fibres is given off from the circum-oral ring to 

 the oral face of each of the tentacles (tnl). Seen in trans- 

 verse section this presents a crescentic figure, lying just 

 beneath the ectoderm cells (PL XVII., fig. 5). The cir- 

 cumoral ring almost completely encloses a tubular space 

 (ts). This, like the nerve ring gives off branches which 



