AMITOSIS IN CILIATED CELLS 109 



and vertebrates, and he states further that because the centro- 

 some cannot ahvays be demonstrated is no reason for concluding 

 that it is lacking. Mitosis, according to this author, occurs 

 exclusively in the ciliated cells of invertebrates. When these 

 cells divide by mitosis the basal granules and cilia are said to dis- 

 appear before division and to be lacking until after division has 

 taken place. He agrees that in vertebrates the sole method of 

 division of ciliated cells is by amitosis. In this process the ciliary 

 apparatus remains unchanged. The difference in the mode of 

 proliferation in ciliated cells of vertebrates and invertebrates, 

 he argues, must be due essentially to the degree of differentia- 

 tion of the cell-plasm. In the development of cilia in cells of 

 embryonic tissue, Saguchi describes a migration of mitochondria 

 from the region distal to the nucleus, where they are grouped, 

 into the cuticle of the cell. Piercing the cuticle, the mitochondria 

 are described as transforming into cilia. In the efferent tubules 

 of the mouse and rat ciliated cells are said to be formed from the 

 cells with brush borders. The mitochondria increase in number 

 and collect distally to the nucleus. They then proceed to the 

 distal cell-border and are transformed into rod-like bodies which 

 sprout short ciha. These ciha pass through the axes of the hairs 

 of the brush border and gradually lengthen. That the ciliary 

 apparatus is formed by the differentiation of the mitochondria 

 and that the centrosome takes no part in the production of ciha 

 are the chief conclusions of Saguchi. 



DISCUSSION 



In general I agree with Peck, and can distinguish frontal, 

 laterofrontal, and lateral epithehum in the gill filament. Peck, 

 however, did apparently not recognize that such a division must 

 of necessity be an artificial one, as the type of cells in these 

 regions varies with their stage of development from the cells of 

 the basal epithelium, so that one type cannot be said to be 

 peculiar to one special region. The cell that Peck described as 

 resembling "a goblet cell with a single coarse flagellum issuing 

 from it," and which he interprets as the large cell of the latero- 



