OCCURRENCE OF AMITOSIS IN MONIEZIA. I I 5 



In my own work I proceeded posteriorly from the neck through 

 the youngest proglottids to the region in which the reproductive 

 organs first appear, and then followed their development from 

 this point to and through the process of maturation. In the 

 primitive germ cells mitosis is more or less frequent, as I have 

 shown in my earlier papers, and if I had not found the most 

 positive evidence of the occurrence of amitosis I should not have 

 doubted that in this period cell division was wholly mitotic. But 

 I found it is impossible to convince myself that this was the case,, 

 simply because I observed too frequently what -I could not 

 interpret as anything but amitosis. 



Richards has not found amitosis in the germ cells, but he does 

 not state what stages in the development of the reproductive 

 organs he has examined. If one may judge from his figures and 

 his statement on p. 313 that " the female sex cells in the cestodes 

 in question are by far the largest cells in the body," it would 

 appear that he has examined only the later stages, in which the 

 cells have already assumed the definite characteristics of germ 

 cells. In these stages I myself have never been able to observe 

 amitosis with certainty, though mitosis is often seen. 



It is during what one might designate as the embryonic de- 

 velopment of the reproductive organs, when the germ cells, at 

 least in the female, are not visibly different, from the cells which 

 form the vitellaria and the reproductive ducts, that I have found 

 amitosis, though even in these stages mitosis sometimes occurs. 

 In order to forestall a possible objection, I should perhaps call 

 attention again to the fact already noted in my earlier work (I., pp. 

 97-109) that after certain stages the portions which are to form 

 the ovary can readily be distinguished from those which are to 

 form vitellaria and ducts by their position and method of growth, 

 though the cells are all still apparently similar. 



Richards says absolutely nothing concerning these earlier 

 stages in his work on Tcenia, and until further evidence is forth- 

 coming, it seems at least possible that his failure to discover 

 amitosis may have been due to the fact that he examined only 

 stages where it does not occur. However, I know nothing from 

 personal observation as to the occurrence or non-occurrence of 

 amitosis in the species which Richards has examined, and since 



