368 YO K. OKADA. 



region is, however, not due to the direction of cutting but is the 

 result of actual proliferation of epithelial cells. Toward the 

 exterior at a certain distance from the fimdus the stratified 

 aspect is no more to be noticed, the cells being generally lower 

 and the secretion less in amount. Thus, in transverse sections of 

 the tubule, the fundus and distal region show a structural differ- 

 ence, the walls of the former being thick and stratified, while 

 those of the latter are thin and simple. Naturally the difference 

 is a gradual one. The caliber and length of the tubules are also 

 variable, but the largest ones are generally situated at the 

 proximal region of the gland. 



A certain quantity of secretion is always found in the tubules. 

 It is granular in composition and readily stainable with haema- 

 toxylin. The epithelium of the tubule is completely destroyed 

 in the process of secretion instead of repeating its function a 

 number of times as ordinary secretory epithelium does. Each 

 cell of the epithelium, in this case, does not function inde- 

 pendently but operates in connection with others along the 

 considerable extent of the walls of the tubule. The new epi- 

 thelium is replaced by the constant proliferation of cells. The 

 process is especially active at the fundus region of the tubule, 

 and here the process is so active that more than one layer is 

 produced before the uppermost one is entirely destroyed. This 

 fact gives rise naturally to the stratified aspect of the epithelium 

 at the fundus region. The nuclei of these cells are ovoid and 

 contain the chromatic substance in normal amount. They do 

 not deteriorate in a degree visible to the eye as far as the cellular 

 destruction occurs. By the time when the cell body is com- 

 pletely disintegrated and the nuclei are set free into the lumen 

 of the tubule, the latter lose their internal structure, their 

 chromatic substance being reduced in amount. Yet the nuclear 

 membrane remains unaltered and shows, adhering to its inner 

 surface, the last scattered traces of the chromatic substance 

 (Fig. 5, n', pi. I.). 



As has been stated, the secretion is of granular constitution- 

 Whether or not the granules are preexistent in the cells is difficult 

 to say. They have been described in the cells of Anomalous 

 and Photoblephalon, two luminous shallow-water fishes in the 



