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granules. Each vesicle which contains excretory fluid 

 and excretory granules ultimately breaks free from the 

 cell and floats away in the excretory fluid. 



In addition to this method, it is highly probable that 

 some of the excretory fluid passes through the epithelial 

 cells into the cavity of the bladder by the ordinary process 

 of diffusion. 



The above mode of excretion is not only performed 

 by the cells of the bladder, but also, according to 

 Marchal, by the cells of the labyrinth, in a slightly 

 modified manner. 



As stated above, the cells of the renal tube in the 

 labyrinth appear to be lined by a thin cuticle. Marchal 

 states that it is not a cuticle, but that the appearance is 

 due to a row of very small vacuoles lining the inner side 

 of each epithelial cell. These vacuoles gradually increase 

 in size, fuse together, and the single large vesicle formed 

 is liberated into the lumen of the renal tube, in a very 

 similar manner to the method described above in the case 

 of the bladder. 



In the cavity of the end sac the fluid contains small 

 vesicles containing yellow oil globules. These have been 

 excreted from the epithelial cells of the end sac, which, 

 as mentioned above, often contain yellow oil globules. 



In addition to these, Marchal states that in Maia 

 entire epithelial cells break free from the walls of the end 

 sac. 



At first Marchal believed that in Maia the wall of the 

 end sac was composed of a single layer of cells, and he 

 expressed surprise that it was possible for cells to break 

 away bodily from such a layer without breaking the 

 continuity of the walls of the end sac. Finally he decided 

 that the wall was several cells thick in certain places, and 

 that it was from these places that the cells found in the 



