36 WRIGHT AND MACALLUM. [Vol. I 



neighborhood of their nuclei, which blacken in the osmic acid 

 of Flemming's fluid, and which may be either fatty or zymogenic 

 in composition ; they are never abundant, and are easily over- 

 looked. (Fig. II.) Apart from this the epithelial cells show all 

 the changes of size, which are exhibited by normal secreting- 

 cells during their life history. The varying thickness of the 

 cells has been given already. This variation is seen sometimes 

 even in the same section ; but in the same specimen it is usual to 

 find that all the epithelial cells from the pharynx to the anasto- 

 mosis of the intestinal branches have a like height. If, now, the 

 intracellular process of digestion occurred in these cells one 

 should hardly expect to find such a variety of thickness when 

 the intestinal contents in every case alike is copious. One would 

 rather believe the difference in thickness to be due to a greater 

 or less waste of the cell-structure, such as is observed in cells 

 secreting a soluble forment. 



In some large forms of Sphyranura, evidently old individuals, 

 the epithelial layer was very thin, so much so that its presence 

 was detectable with difficulty. In our series of sections it was not 

 possible for us to say that those which exhibit a thin epithelial 

 layer were made from such old individuals ; nevertheless, we 

 believe that this decrease in thickness goes on gradually with 

 advancing age, and that the cells are not renewed, but persist 

 throughout life. For, although we have often determined the 

 presence of cell-division in all the other organs of the body, 

 yet not one case of this was observed in the intestinal epithelium. 



The Reproductive Organs. 



The diagram (Fig. 13) will serve to elucidate some points in 

 the arrangement of the sexual organs not clearly shown in 

 Fig. I. Sphyranura is hermaphrodite; but the male and female 

 organs are quite independent of each other, although there exists 

 a tube, interpreted by Zeller as an internal connecting tube 

 between the two, the true nature of which has, however, only 

 recently been explained by Ijima.^ 



The male organs comprise the testes, vas-deferens, ejacula- 

 tory bulb, and its terminal part, with the coronet of spicules. 

 The female organs comprise the ovary, oviduct, and ootype, 

 from which there lead the ducts to the right and left recep- 



' Zool. Anzeig., VII., 635. 



