The Histogenesis of Cysticercus pisiformis. 211 



a ganglion drawn under low power, while in Fig. 52 are shown 

 three ganglion cells enlarged. The protoplasm is coarsely granular and 

 is indistinguishable from that of the formative cells to be discussed 

 later under Cytogenesis. A fibrillar structure of the protoplasm is 

 suggested, however, in part of the ganglion, but this could not be 

 indicated in the figure. The entire ganglion is traversed by paren- 

 chyma fibres, and a few scattered muscles are seen passing thru it. 

 At X in Fig. 65 is shown a typical parenchyma cell with an attached 

 nerve cell. These two cells are shown enlarged in Fig. 53. The 

 former consists of a deeply stained nucleus with a few fibres radiating 

 from it. The granular protoplasm at one end of this cell has 

 evidently been deposited by it and a nucleus has developed therein. 

 The protoplasm is seen extending in a long thin process toward the 

 developing ganglion. The question may be raised as to what evidence 

 there is to show that this is a nerve cell. The only evidence is its 

 proximity to the ganglion toward which is extending its cytoplasmic 

 process, and the similarity in its structure to the ganglion cells. 

 But the question may be further asked how one can determine that 

 this mass of cells is a ganglion rudiment. The evidence here is 

 its position, the suggestion of a fibrillar structure in part of the 

 granular protoplasm, and the evident similarity between the cells 

 composing it and those of an unquestionable ganglion in a slightly 

 later stage. But in the cells shown in Fig. 53, how is one to know 

 which is primitive and which derived? I think that the answer 

 to this question will be evident when we come to consider cyto- 

 genesis. The nucleus lying in the granular cytoplasm is evidently 

 more recent than that which constitutes the great bulk of the 

 parenchyma cell. Further, the direct attachment of the latter to 

 the parenchyma network and the unattached relation of the former 

 lying as it does loosely among the parenchyma fibres which traverse 

 its cytoplasm, but do not attach themselves to it, gives evidence of 

 the priority of the latter over the former cell. Whether the paren- 

 chyma cell will itself become diiferentiat«d into a ganglion cell or 

 not, there is no evidence to show. 



An idea of the variation in size of the developing ganglion 

 cells, some measurements of which Avill be given later may be ob- 

 tained from Fig. 52. 



A part of one of the lateral cephalic ganglia in a later stage 

 of development is shown in Figs. 62 and 63. In the latter is seen 

 a group of developing ganglion cells lying between two masses of 



