108 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



fig. 3, PL I, which is based on a reconstruction from 

 serial sections. I am not at all sure that it is accurate 

 in all details, for the difficulty in the investigation of the 

 nervous system of Cestodes is that the fibrils stain only 

 with great difficulty, or not at all. What has stained in 

 the series of sections studied is the parenchyma, with the 

 ganglion cells, and it is these tissues that are represented 

 — of true nerve tracts there was no indubitable indica- 

 tion in the preparations. But ganglion cells were 

 certainly present in the main cerebral mass, and some Of 

 these bodies are represented in fig. 1, PI. I. They 

 are typical bipolar or multipolar cells of variable size 

 with characteristic nuclei. They are usually situated in 

 spaces, the boundaries of which appear to be fine 

 reticula, with some nuclei. The processes of these 

 ganglion cells can be traced for a very short distance 

 only, and they appear to fray out into fine fibrils. The 

 tissue in which they are embedded is a modification of the 

 parenchyma, with a closer meshwork, and a rather more 

 intense staining reaction than elsewhere in the body. 

 Part of this ground tissue appears to consist of exceed- 

 ingly fine fibrils running in all directions, but whether 

 or not this is truly nervous and not neuroglial is difficult 

 to determine. 



The central ganglionic mass lies immediately behind 

 the strong dorso-ventral muscle bundle referred to above 

 as joining together the bothridial suckers. It is really a 

 commissural mass crossing the body from side to side, in 

 the middle line, and between the dorsal and ventral 

 proboscis sheaths (fig. 5, PI. I). Four nerves take 

 origin, each by several " roots," at the lateral anterior 

 margins of this ganglionic mass, and these — the both- 

 ridial nerves, in other Tetrarhynchids, run outwards and 

 forwards into the scolex. Two large nervous strands take 



