24 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



returning owing to the vibration of the cilia of the wall of the obtype. 

 This initial portion of the uterus is more or less completely covered 

 by a mantle of apparently undifferentiated cells (Plate 4, Fig. 42). Juel 

 ('89) finds similar cells in Apoblema excisum, which, however, appear 

 from his description and figure to form a more or less compact mass 

 through which the uterus passes. He regards the cells as the remnants 

 of the primitive meristem cells which formed this part of the sexual 

 organs and thinks that they have remained here comparatively undif- 

 ferentiated. I do not see why they could not equally well be regarded 

 as parenchyme cells which for some reason have retained near this 

 portion of the uterus their primitive character. As Juel states, they 

 certainly do not appear to be gland cells. The wall of the uterus 

 appears to be a thin structureless membrane from which nuclei can oc- 

 casionally be seen projecting into the lumen. In some places I have 

 been able to distinguish circular and longitudinal muscle fibres, which, 

 however, are very delicate and placed some distance apart. The eggs 

 undergo development to a considerable extent in the uterus, but on 

 account of the included yolk it was found very difficult to follow the 

 process satisfactorily. 



Owing to lack of time and inability to obtain fresh specimens for the 

 employment of special methods, no extended observations were made on 

 the nervofts system. Numerous sensory papillas, similar to those de- 

 scribed by Bettendorf ('97), were observed in the oral and ventral 

 suckers and at the anterior end of the body. Two of the largest of these 

 appear to be constant and are symmetrically placed at the anterior end 

 (Fig- 1). 



