366 LEWIS HENRY GOUGH. 



of the dorsal canal have a common origin — the epithelial cells 

 of the excretory system. 



The Nervous System. Figs. 38-40. 



The central nervous .system of the strobila consists of a 

 nerve lying lateral to tlie ventral canal on either side of the 

 strobila. From this main nerve bra.nches are given off in 

 every segment, which are, liowever, very difficult to observe. 



The nerves on entering the scolex first bend inwards, 

 passing- well into the central space enclosed by the suckers. 

 At the level of the bottom of the hollow of the suckers four 

 ganglia are found, two lying in the inner lateral angles formed 

 by the suckers, two in the inner median angles. These four 

 ganglia are connected by transverse commissures, so that the 

 lateral ganglion of each side is connected to both the dorsal 

 and the ventral median ganglia ; the ganglia are further con- 

 nected by a transverse commissui'e, connecting the two lateral 

 ganglia, and a dorso-ventral commissure, connecting the two 

 median ganglia. The transverse and the dorso-ventral com- 

 missures fuse in the middle of the scolex, where they cross 

 each other and form a central ganglion. Each of the four 

 peripheral ganglia gives off two nerves, which proceed at first 

 anteriorly and then bend over and unite with the nerve of the 

 neighbouring ganglion, the eight nerves thus forming four 

 loops connecting the four ganglia. Anterior to these is a 

 second central nerve-plate, poorer in ganglion cells, whose 

 connection with the rest of the nervous system has not been 

 made out. 



The histology of the nervous system presents on the whole 

 the usual structures. The lateral nerves in the strobila 

 consists chiefly of neurofibriliio, arranged parallel to each 

 other on longitudinal sections, having a reticulated appear- 

 ance on transverse sections. The neurofibrillas are accom- 

 panied by scattered glia cells, which are chiefly found on the 

 surface of the nerve. Ganglion cells were vei-y rarely observed 

 in the nerves of the strobila. 



