THE METHOD OF CELL DIVISION IN MONIEZIA. 



C. M. CHILD. 



Since the appearance of Richards's paper on the method of 

 cell division in Miuiiezia (Richards, 'n) Dr. Richards, in answer 

 to a request of mine, has very kindly permitted me to examine 

 some of his slides of early stages in the development of the ovary 

 and of cleavage stages, with the privilege of publishing the re- 

 sults. The present paper consists of a brief statement of the 

 results of my examination of these slides, together with some 

 consideration of recent criticisms of my observations on amitosis. 

 I take this opportunity of acknowledging my indebtedness to 

 Dr. Richards and also of acknowledging an error of my own 

 which though it does not directly concern the chief point at 

 issue certainly requires correction. Dr. Richards is undoubtedly 

 correct in his statement that the early cleavages in Moniezia 

 are mitotic, either entirely, or to a much greater degree than my 

 earlier statements would indicate. With this acknowledgment 

 of my error the chief point of disagreement between Richards's 

 positive observations, so far as they go, and my own is removed. 

 The difference between us seems to me to rest no\v on Richards's 

 failure to recognize, or to interpret as I have done, what the 

 material actually shows. 



The whole problem of amitosis seems to me somewhat un- 

 profitable at present as a subject for investigation on a purely ob- 

 servational basis. Experimentation is necessary be- fort- we can 

 reach any certain conclusions as to the significance of either mitosis 

 or amitosis in the life of the cell. Moreover, cytological thought 

 is at present dominated by morphological hypotheses, which are 

 themselves based on direct observation rather than on experi- 

 ment. So long as this remains the case all observations which do 

 not accord with the current hypotheses will be explained a\\,i\ 

 by one course of 'reasoning or another and brought into agreement 

 with ihesc hypotheses. So long then as our conclusions are 

 b;i~<-(| Dimply upon observation in fixed material and without any 



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