METHOD OF CELL DIVISION IN MONIEZIA. 149 



in the middle of the anlage that these ducts develop. In the 

 vagina it is not certain that the parenchyma cells whose position 

 it occupies were numerous enough to provide all the cells in its 

 walls without the aid of some outward growth from the region 

 already formed. There is no fundamental difference, however, 

 in the two methods for in either case the cells are of parenchymal 

 origin. 



The conditions in the early primary anlage have already been 

 set forth. Mitoses are few, but they do occur. There is no 

 certain evidence for amitosis although many nuclei are arranged 

 in pairs. I have previously given my reasons for the view that 

 amitosis does not occur at this stage of development. 



But in the stages beginning with those in which the anlagen 

 of the various organs can be distinguished the method of cell 

 division can be conjectured only. Mitoses are very few, in- 

 deed, and occur only in the borders of the proliferating region. 

 On the other hand, the nuclei are small and irregular in size and 

 are frequently closely crowded together in groups of two, three or 

 even more. My preparations do not show actual cases of ami- 

 tosis, however, although conditions would seem to be quite 

 favorable for its occurrence. Other than the rare mitotic figures 

 which occur there is absolutely no evidence as to the method 

 of nuclear multiplication (see Figs. 51 and 52). 



The opinions with regard to the regions in which active cell 

 divisions are occurring expressed by Child ('07^) in the following 

 statements do not seem to be well founded according to my 

 observations. He says: "In the early stages there is a marked 

 difference in the size of the nuclei in the central and the peripheral 

 portions of the area in which proliferation is occurring. . . . 

 Evidently proliferation is much more active in the central than 

 in the peripheral regions of the proliferating area. In somewhat 

 later stages the rapidity of division apparently decreases and the 

 nuclei of the central regions gradually increase in size until they 

 are almost or quite as large as those about the periphery. . . . 

 From this stage on the differentiation of the walls of the ducts 

 gradually takes place: muscle fibers develop, a lumen appears, 

 and nuclear divisions become less and less frequent." 



In this quotation (the omitted parts have to do only with 



