The Histogenesis of Cysticercus pisiformis. 237 



diameter entirely apart from any other granules. 

 Furthermore in thousands of nuclei examined I have 

 never yet been able to see a granule that was un- 

 doubtedly in a state of division. It is true that I have 

 seen such a lobed granule (as is shown at x in Fig. 13) and it is 

 possible that this is a dividing granule, but it is also possible that 

 it represents an agglomeration of several granules, rather than the 

 division of a single one. Such cases are the exception and not the 

 rule, however, and while they render possible an interpretation of the 

 phenomena observed by the assumption of a 'division of granules in 

 some cases, they cannot overthrow the evidence offered by those 

 very small granules which are found entirely separated from 

 all others, not only in the same section but in adjacent 

 ones. 



Further evidence in support of the theory of an independent 

 origin of granules from a cytogenic protoplasmic mass is offered by 

 the cell shown in Fig. 11. Here one sees a granule, which is less 

 dense on one side than on the other, surrounded, as is usually the 

 case, by a clear zone in the protoplasm. I interpret this as a 

 developing granule which has not yet acquired the same density 

 thruout. The nuclear membrane is well formed about part of the 

 cell, but incompletely formed about other parts. This cell was 

 selected from a young larva and was so situated that I could 

 determine that it was entirely isolated from all other cells. 

 Here then is an evidently immature nucleus containing an immature 

 granule, which is developing entirely apart from all other nuclei or 

 granules. 



I have not been able to find a single instance of mitosis in 

 either Cysticercus pisiformis or Taenia serrata.^) Ina few in- 

 stances however I have seen some evidence of the origin of new 

 nuclei by the division of a pre-existent nucleiis. Such a case is 

 represented in Fig. 5. Here are seen two distinct, darkly stained 

 granules lying in the nucleus, while between them is a distinct line, 

 with two or three small swellings. This line is apparently a new 

 nuclear membrane arising to separate the old nucleus into two parts. 

 The condition here presented is not fundamentally different however 

 from that already described, the only difference being that here two 

 granules became surrounded by a common membrane at first, to 



1) See Appendix. 



