The Histogenesis of Cysticercus pisiformis. 235 



In Fig-. 10 is represented a small portion of the wall of the 

 larva at a stage in which the scolex rudiment is just forming. It 

 shows a large mass of cytogenetic protoplasm, mcij, containing three 

 developing nuclei. In two of these the nuclear membrane is well 

 formed, while the third is represented only by a single large, densely 

 stained granule. It is interesting to note here the diiference pre- 

 sented by the two young nuclei and the three older nuclei in the 

 meshes of the parenchyma above. The three latter are filled with 

 granular nucleoplasm which appears identical with, tho possibly a 

 little deeper stained than, the cytoplasm outside the nucleus. The 

 two former contain but a very few granules of nucleoplasm and are 

 consequently very lightly stained. The darkly stained granule lies 

 free in the granular cj^toplasm. 



Fig. 12 shows a group of nuclei developing from a central mass 

 of protoplasm which has nearly been used up in the manufacture of 

 the nuclei already formed. The two cells, x, x^, are probably very 

 early stages of flame cells, the upper unquestionably so. A curious 

 appearance is presented by x^. This nucleus shows at its two 

 opposite poles two triangular-shaped, densely-staining masses, x shows 

 a single such mass at the pole opposite to that at which the basal 

 plate and ciliate process are developing. This structure is frequently 

 observed in developing flame cells and others. Its significance is 

 doubtful. So far as I can judge, it is merely a thickening of the 

 nuclear membrane without any special significance. It is possible 

 that it represents a reserve supply of chromatin to be later used 

 up in the economy of the cell. The significance of the three darkly- 

 stained processes attached to x.. is likewise uncertain. Four of the 

 cells x, Xi, Xo, x^ have already been constricted ofl' from the parent 

 mass of protoplasm ^), a fifth cell x^ has been partly constricted off, 

 while the sixth ^'5 is just developing a nuclear membrane about its 

 three darkly-staining granules. Close to this nucleus lies a very 

 small granule whose meaning is uncertain, but it is probably similar 

 to the granules in x-^. In four of these nuclei there is evident a 

 narrow lightly-stained zone surrounding the contained granules. 

 The other two nuclei do not show it. 



Another group of developing cells is represented in Fig. 6. 



1) I have no means of determining absolutely that all of these cells 

 have been formed from this mass. Their close proximity to , and union 

 with it, however, renders this supposition probable. 



