STUDIES ON CILIATED CELLS 251 



C. ELIMINATION OF CILIATED CELLS 



In the epithelium of the intestine of Anodonta it is often seen 

 that some cihated cells are being shed into the lumen. In the 

 nuclei of such cells there appear numerous nucleolar corpuscles, 

 while the nuclear sap becomes increasingly darker ; that is to say, 

 the nucleus is in the state of nucleolar hyperchromasy ; in the 

 cytoplasm, in addition, numerous larger or smaller vacuoles make 

 their appearance, so that the whole exhibits a phenomenon of 

 degeneration. 



VI. REGENERATION OF CILIATED CELLS 



As the ciliated cells are reduced in number in the manner 

 above mentioned, it is natural that they must be replaced by 

 new ones. This is carried out either by the transformation of 

 different kinds of cells into ciliated, or by the division of ciliated 

 cells themselves. 



A. TRANSFORMATION OF OTHER KINDS OF CELLS INTO CILIATED 



CELLS 



That ciliated cells are derived from replacement cells, was 

 noticed by Drasch ('81), Flemming ('85), Bockendahl ('85), 

 Joseph ('05), Tschassownikow ('13) and others. According to 

 these authors, the mitotic figures which often occur in the cil- 

 iated epithelium, do not belong to cihated cells themselves, but 

 to cells of different nature, especially to replacement cells, which 

 form a source of cihated cells. Schnitzler ('93), on the con- 

 trary, admits the transformation of goblet cells into ciliated. 



I have observed, in the efferent tubule of testis of the adult 

 mouse and rat, that ciliated cells are derived from neighboring 

 non-ciliated, with which process I shall deal later in the chapter 

 on the development of the ciha. 



B. MITOSIS OF CILIATED CELLS 



Although the question as to whether the ciliated cell mul- 

 tiplies by mitosis or not, has received much attention, it is still 



