376 WM. L. TOWER, 



these pass mediad, one above, the other below the excretory tube, 

 crossing the proglottis to the correspouding regions of the ganglion 

 of the opposite side. These two nerves are the dorsal and the ventral 

 commissures (PI. 22, Figs. 6 and 7 corns, d and corns, v). They are 

 loose, band-like nerves flattened dorso-ventrally, and plentifully sup- 

 phed with ganglionic cells, either singly or in groups, at points where 

 nerves are given oft'. The ganglionic cells are almost always of the 

 bipolar type (PI. 24, Fig. 20), but otherwise have the same character- 

 istics as the ganglionic cells from the other parts of the nervous 

 system. I have not found any binding cells along the dorsal com- 

 missure, and from its loose texture it is doubtful if any exist. 

 This nerve in its passage across the proglottis lies slightly behind 

 the transverse excretory tube and among the transverse muscles, 

 some of which frequently run through the substance of the nerve. 

 Because of this peculiarity the nerve is often so broken up and con- 

 cealed by the bundles of muscles that it is difficult to trace its course. 

 In places it appears as a moderately compact nerve, but it may 

 shortly become a mere tangle of nerve and muscle fibres, from which 

 it may emerge as a broad sheet of nervous tissue. This nerve is 

 inconstant in form, like all the nerve structures excepting those of 

 the scolex and the lateral nerves. Its inconstancy of form is due, I 

 beheve, to the fact that the nerve elements lie embedded in the tissues 

 of the body without any protective structure to bind them into a 

 compact nerve. 



From the outer edge of the posterior lateral ganglion there 

 arises a cluster of nerve fibres, the largest and most important of which 

 is the marginal nerve (n. marg). This arises from the anterior portion 

 of the outer edge of the ganglion, passes outward and then anteriad 

 through the greater part of the margin of the proglottis (PI. 22, 

 Fig. 6, PI. 23, Fig. 12). A short thick nerve arises from the posterior outer 

 edge of the ganglion, and passes posteriad into the proglottis, which 

 lies immediately behind that in which the ganglion is located. A 

 cluster of still shorter branching nerves arises from the lateral margin 

 of the ganglion between the marginal and the posterior nerves and 

 is distributed to the outer posterior angle of the proglottis. 



The posterior lateral ganglion is made up of a mass of ganglionic 

 cells and a great number of nerve fibres intermingled in a most 

 confusing manner. Transverse sections of the proglottis in the 

 plane of the dorsal and ventral commissures (PL 25, Fig, 28 and 

 PI. 26, Fig. 31) are the most instructive, although frontal sections 



