508 WARO NAKAHARA 



complete series of changes. This will, however, remain as an 

 open question for future study. 



The studies of Child ('04, '07 a, '07 b, '11, ''l2) and of some 

 others of similar nature are valuable, especially because it is 

 largely due to these works that theories of physiology underlying 

 cell-division began to develop. Their data indicate that amito- 

 sis occurs, not only in the regions where a secretion is elaborated 

 or a reserve material is formed, but also in rapidly growing tis- 

 sues, and it was largely this latter fact that led these authors to 

 conceive amitosis to be a normal, but rapid, method of cell- 

 multiplication. There are, however, several observations which 

 make us hesitate to accept the claimed occurrence of amitosis in 

 the regions of rapid growth. Young ('08, '10, '13), studying the 

 histogenesis in some cestodes, thinks that the rapid multiplica- 

 tion of the cells is due to what he calls 'de novo' formation of 

 new cells. He observed that the daughter cell is formed from 

 an irregular mass of coarsely granular cytoplasm, containing 

 numerous small, deep staining granules, around which, later, 

 nuclear membrane arises, and finally, together with a small mass 

 of c3^toplasm, separates from the mother mass. Richard ('11), 

 in his work on Moniezia, could not affirm whether mitosis or 

 amitosis is the method of cell-multiplication in that form. Har- 

 man ('13) was also unable to decide the method of cell-multipli- 

 cation in her work on Taenia and Moniezia. Finally, Paxman 

 ('15) described accurately the process of rapid cell-multiplica- 

 tion in the sub-cuticula of Dilepis by the development of pro- 

 toplasmic masses similar to that observed by Young. Paxman, 

 after a careful examination of 10,000 nuclei in the region, decides 

 strongly against the occurrence of amitosis or mitosis. It may 

 not be safe, therefore, to draw any conclusion from such cases of 

 amitosis as are claimed to occur in rapidly growing tissues, at 

 least not until such cases are brought under clearer light. 



The data derived from experimental studies are very interest- 

 ing. However, 'amitosis' produced by means of certain chemi- 

 cals may be easily explained, if we assume, with Jordan ('13 b), 

 a 'stupefying' effect of the chemicals upon the kinoplasm, be- 

 cause this will make it impossible for the dividing cells to show 



