374 WM. L. TOWER, 



ganglionic cells others which do not appear to have any nerve fibre 

 connected with them. These cells are richly branched, the branches 

 interlacing with the dentritic processes of the ganglionic cells. It is 

 impossible to say whether they act as a means of connection between 

 different neurons, whether they are developing ganglionic cells, or have 

 some other function. One of these cells is shown very faintly in 

 PI. 26, Fig. 32. In this region the dorsal and ventral commissures 

 have become in so far complete that they can be traced from the 

 posterior lateral ganghon of one side to that of the other. The 

 ganglia of the dorsal and ventral nerves have also begun to be 

 distinguishable, but there is as yet no trace of the anterior lateral 

 ganglion, nor of the genital or marginal nerves. At least it has not 

 been possible by any method which I have used to demonstrate their 

 presence until after the dorsal and ventral commissures, as well as 

 the dorsal and ventral ganglia, have made their appearance. 



3. In the Mature Proglottis. 

 In each lateral half of every proglottis there is, besides the 

 dorsal and the ventral commissures and the large lateral nerve, a 

 dorsal and a ventral longitudinal nerve, an internal and an external 

 genital nerve, and a marginal nerve. The lateral nerve trunk is im- 

 bedded in the parenchyma of the body, from which it is not sharply 

 defined; it is elliptical in cross-section, the larger axis of the ellipse 

 having a dorso-ventral direction. The course of these nerves is nearly 

 parallel to that of the longitudinal excretory tube (PI. 22, Fig. 6 n. 1). 

 The nerve is a compact bundle of naked axis cylinders separated 

 from one another by a structureless hyaline matrix, the whole being 

 bound together by peculiar binding or protecting cells like those found 

 in the scolex. These cells appear elliptical in outline, and send out 

 a considerable number of branching processes that run over the sur- 

 face of the nerve, and serve, I believe, to bind the nerve fibres into 

 a compact bundle and to separate them in a measure from the tissues 

 in which the nerve is imbedded (PL 25, Fig. 30 cl.vin). These 

 branches are not, however, so numerous nor so dendritic in character 

 as in the cells of similar function figured by Zernecke (1896, tab. 13, 

 figs. 55, 56) for Ligula. In longitudinal sections of the nerve they appear 

 lenticular, the edges being prolonged for a considerable distance over 

 the surface of the nerve trunk. In some regions they lie singly, separated 

 from each other by a considerable distance; in others they lie close 

 together, as seen in Figs. 9 (PI. 22) and 15 (PI. 24). There seems to be no 



