2]^ 2 Robert Thompson Young, 



granular protoplasm in which the nerve fibres of two of the future 

 nerve tracts of the ganglion are being- differentiated. The ganglion 

 is traversed, as in the earlier stages, by parenchyma fibres and a 

 few scattered muscles. Imbedded in it are seen two heavily- stained 

 parenchyma cells, pc. The principal points in which this stage shows 

 an advance over the preceding are the greater size of the ganglion 

 cells and the more distinctly fibrous nature of the cytoplasm. The 

 fibres vary considerably in size and the cells show great variation 

 both in size, shape and chromatin content. Most of the developing 

 cells in these ganglia lack distinct polarity since the cells in this 

 stage are simply indefinite masses of formative protoplasm ; and the 

 same is true, of many of the cells, in the ganglia of the scolex and 

 immature proglottids of Taenia serrata. As Fig. 63 shows, a few 

 of the cells lie in the fibre bundles at the sides of the ganglion, 

 but the majority of them lie between these bundles. 



Figs. 62 and 63 show very clearly that the primitive nerve fibres are 

 continuous with the granular protoplasm of the ganglion cells. That 

 they are not, however, developed as outgrowths from 

 pre-existent ganglion cells, but rather as a fusion of 

 individual protoplasmic granules in a mass of proto- 

 plasm elaborated by the primitive neurogenic paren- 

 chyma cells, is evidenced by the fact that the fibres may be 

 very plainly seen to be developing in this protoplasmic mass. The 

 same method of formation of nerve fibres is evident at different 

 points along the main nerve trunks in Taenia serrata (Fig. 64). It 

 probably also occurs in the smaller nerve trunks, but this point has 

 not been investigated. In such a stage as is represented in Figs. 62 

 and 63, there are as yet no fully developed nerve fibres in the 

 neurogenic protoplasmic mass. The protoplasmic granules may, how- 

 ever, be seen arranging themselves in more or less definite lines. 

 It is by the fusion of these primitive granules that the fibres in 

 the ganglia and main trunks of the scolex are developed. The 

 ganglia in the scolex and neck of Taenia contain the same granu- 

 lar protoplasm as the ganglia and nerve trunks of Cysticercus. It 

 is also present in the ganglia of the nerve cords even in pro- 

 glottids in which the reproductive organs are well established. It 

 is, apparently, a strictly embryonic condition, as the nerves in the 

 mature proglottids do not show it. In this connection the account 

 of PiNTNER (1880, p. 231) of the difference between the nerves in 

 the scolex and those in the proglottids of Tetrarhynchus longi- 



