STUDIES ON CILIATED CELLS 249 



Summary 



1. Ciliated cells are transformed into non-ciliated columnar 

 and glandular cells. 



2. In the transformation of the ciliated into the glandular 

 cell, the cilia disappear, either before or after the accumulation 

 of secreted material. 



3. The disappearance of the cilia is not by withdrawal but by 

 the'r being cast off. 



B. ATROPHY OF CILIATED CELLS 



That ciliated cells undergo atrophy, without being cast off, I 

 have noticed in the gall-duct of Rana temporaria. The first 

 change which occurs in the cell is nuclear hyperchromasy 

 (compare my previous paper, 1915) : there appear in the nucleus 

 numerous nucleolar granules, stained black by iron-haematoxy- 

 lin, just as the nucleolus. With the increase of these corpuscles 

 in number, the nuclear sap comes to stain more and more darkly, 

 so that at last the nucleus becomes entirely a black mass. The 

 cytoplasm also sooner or later grows black, especially in its 

 upper portion (fig. 58, 59). In the course of time the black mass 

 grows more and more pale (fig. 60) and then there can be seen 

 in the cytoplasm numerous, larger or smaller round or oval 

 black corpuscles, which often are so numerous as to hide the 

 nucleus entirely from view; the chondriocontes which were 

 found before, have now disappeared. I think that the cor- 

 puscles in question are derived partly from degenerated chon- 

 driocontes, partly from the nucleolar granules passed out of the 

 nucleus. While the cytoplasm still is in the state of heavy nu- 

 cleolar hj^perchromasy, the cell in question becomes constricted 

 at the upper part, below the cuticle, two pieces, the upper 

 smaller and the lower larger one, being thus produced (figs. 59, 

 60). Then the connection between the two becomes lost; the 

 upper cihated one is, in all probabihty, cast off into the lumen. 



The ciliated corpuscles, first found by Neumann and then 

 recognized by Schmidt ('82) must be remembered in this con- 

 nection. These corpuscles, according to Neumann, bear cilia, 



JOURNAL OF MORPHOLOGY, VOL. 29, NO. 1 



