CELL DIVISION IN T.ENIA. 323 



do not believe that it is borne out entirely by the facts. In Tienia 

 the parenchymal cells are relatively less in number in the old 

 tissue than in the younger, a relation which is only partially ex- 

 plained by the fact that other kinds of cells develop from the 

 parenchyma. On the other hand, the ground substance in the 

 young proglottid is more spongy and less in amount than in the 

 older portions of the animal. These observations show that the 

 growth of the parenchyma is not due alone to cell multiplication 

 but also to the formation of new intercellular matter and to the 

 greater development of the cytoplasmic strands. The growth of 

 the cestode soma is due chiefly to the growth of the parenchyma 

 and of the muscle cells and fibers. Other tissues, except the sex 

 products, are practically negligible in accounting for increase in 

 size. With regard to the growth of the muscle fibers a similar 

 condition obtains in them as in the parenchyma, as is shown above. 

 Thus we find growth depending not so much on the increase in 

 the number of cells as in the increase in amount of products of 

 cellular activity, that is, in fibers and intercellular material. 

 Therefore, the rapidity of growth in the cestode body does not 

 necessarily postulate a large number of dividing cells. 



As to the method of cell division little can be said. No 

 traces of amitosis appear. Cases of several nuclear divisions in 

 a common cytoplasmic mass s\ich as are figured by Child (ii) 

 for Monieza are not to be seen in T&nia, nor is any explanation 

 of them afforded by the latter genus. I have also observed no 

 cases of mitosis. The evidence at hand, I believe, does not 

 warrant any conclusion as to the method of cell division in the 

 parenchyma of this form. 



SUMMARY. 



1. Amitosis has not been found to occur in the oogenesis of 

 the cestodes studied. 



2. All observations on the process of oogenesis point to mito- 

 sis as the usual method of cell division. 



3. The presence of a " Nebendotter " which has peculiar stain- 

 ing properties gives a misleading appearance of amitosis. 



4. Maturation is of the typical form. 



5 . Indirect evidence strongly suggests that physiological factors 

 influence the frequency of mitotic divisions. 



