320 



A. RICHARDS. 



in specialization and a loss in reproductive potentiality. Rapidity 

 of division in these cases is a negligible factor. We are simply 

 dealing with a special case under the old theory, if amitosis be 

 found to obtain here. Amitosis, then, may well be expected in 

 these systems. 



The facts observed in the genitalia of TcRnia do not bear out 

 fully that expectation. The structure of the genital ducts and 

 organs can be made out clearly and nuclei, cytoplasm, and inter- 

 cellular substance seen. Yet cases of amitosis have not been 

 demonstrated. On the other hand, a mitotically dividing nucleus 

 is found only rarely. This may mean that mitosis is of very 



FIG. 15. Second oocyte; early anaphase, spindle stained very lightly. Figs. 

 15-17 show the large cytoplasmic granules. 

 FIG. 16. Second oocyte ; telophase. 



short duration, or more probably, that it is of short duration and 

 occurs in waves ; or, again, it may indicate that the nuclei divide 

 amitotically. But whichever interpetation we may accept we do 

 no violence to the theory of Ziegler and vom Rath. 



The muscle-cells also furnish only negative evidence of ami- 

 tosis. They are large, spindle-shaped cells from which contractile 

 fibers extend. The cytoplasm is densely reticulated, rarely ex- 

 hibiting the vacuolated structure described by Child (8). The 

 quantitative relations of cells and fibers at different periods of de- 

 velopment are of interest. Relatively more muscle cells are 

 present in a young proglottid than in an old one, but the muscle 

 fibers are much more developed in the later stages. The sig- 

 nificance of this relation, which agrees closely with a similar pa- 

 renchymal relation, will be discussed later. While satisfactory 

 evidence as to the usual method of cell division has not been 

 obtained, the observations on the material at hand favor mitosis 

 as typical. 



