STUDIES ON THE ECTOPARASITIC TREMATODES OF JAPAX. 103 



one or several nucleoli. The eiferent ducts are exceedingly long and 

 variously cross each other in their course. When the cells are active 

 these ducts are filled with a weakly staining, granular substance 

 exactly like in apyjearance to that of the cells themselves. In this 

 case their wall is very distinctly visible, but in the intervals of 

 secretion it seems to collapse entirely, and the ducts are then no 

 more visible. 



In the genus under consideration the prostate glands enter the 

 penis at its base a little towards one side (PI. XXII, fig. 2), and open 

 into its cavity. Just before entering the penis, the ducts are often 

 filled to such a degree as to be partially stopped up, and at this point 

 often present in consequense a ruggedly swollen appearance (PI. XXY, 

 fig. 8). 



In Epibdella I have observed a pair of peculiar egg-shaped organs 

 on either side of the median line just behind the testes (PI. XXV, figs. 

 4 & 6, x). In sections they are seen to be a mass of polygonal cells, 

 each of which contains a nucleus with a nucleolus, and has a coarsely 

 granular, slightly staining cytoplasm (PL XXVI, fig. 8), the whole 

 mass being provided Avith a distinct limiting membrane. Judging 

 from their appearance and reaction towards staining fluids I should 

 consider them as glands, but I have not been able to find out any 

 duct or any connection with the neighboin-ing organs. 



(b). The Female Organs. 



Ovary — The ovary is always single and is simply a cavity in the 

 mesenchyma filled with germ-cells. Unlike what is seen in the 

 testes, however, the cavity is usually bounded by a thin membrane of 

 connective tissue, closely applied to which are sometimes observed 

 oval or flattened nuclei (PI. IV, fig. 8); but these are in my 

 opinion to be regarded as the nuclei of the mesenchyma, and not as 



