STUDIES ON CILIATED CELLS 261 



6. It seems probable that there exists some connection be- 

 tween the centrosome and the amitosis. 



D. SIGNIFICANCE OF MITOSIS AND AMITOSIS OF CILIATED CELLS 



As mentioned above, there are two methods of division of the 

 cihated cell, mitotic and amitotic. Mitosis occurs only in in- 

 vertebrates; in vertebrates I have never been able to find it. 

 Those who accept the hypothesis of Henneguy and Lenhossek, 

 assert that the absence of mitosis in ciliated cells is a consequence 

 of the lack of the centrosome. I do not agree with this, for the 

 centrosome can easily be detected in ciliated cells in which mi- 

 tosis does not occur. On the contrary, amitosis is the sole 

 method of division of ciliated cells of vertebrates, in spite of the 

 presence of the centrosome. 



As to the significance of amitosis, two distinct and opposed 

 views are held by histologists. According to one view, urged 

 strongly by Flemming, Ziegler, and vom Rath, amitosis is not 

 accompanied by the cytoplasmic division, but such a cell degen- 

 erates sooner or later. That the nuclei of degenerating cells 

 may multiply by amitosis has received much attention (Nissen 

 '86, Heidenhain '90, Plate '98, Dobell '07, Reichenow' 08) ; and, 

 in fact, I have also noticed that the nucleus multiplies by direct 

 division, in the degeneration of certain glandular cells in the 

 larval epidermis of some Amphibia (Saguchi '15). 



On the other hand, Child ('07), Patterson ('08), Maximow 

 ('08), Des Cilleules ('14) and others affirm that amitosis is not 

 always degenerative, but can be accompanied by the actual cell- 

 multiplication; and, that mitosis follows amitosis and vice versa. 

 According to Child and Patterson, amitosis is in close relation 

 to the rapid nuclear multiplication and accordingly to the growth 

 of tissues. Child, in addition, remarks as to the occurrence of 

 amitosis as follows: ''Moreover, in several cases I have noted 

 that in growing tissues where nuclei of different size are present, 

 mitosis seems to occur more frequently in larger nuclei sur- 

 rounded by considerable undifferentiated cytoplasm, while ami- 

 tosis is more characteristic of the smaller nuclei with scanty 

 cytoplasm." Recently, Jordan ('13) described ciliated cells 



