28 WRIGHT AND MACALLUM. [Vol. I. 



mens of this form were hardened in Flemming's fluid, stained 

 with alum-cochineal and sectioned in the manner already- 

 detailed. The cells in the oral sucker are few in number, not 

 more than five or six, there being a much larger number, on 

 the other hand, in the caudal sucker. Those of the oral sucker 

 have usually a definite globose or spherical form, while those of 

 the caudal sucker are pear-shaped, elongated oval, or more or 

 less flattened by the parallel muscular fibres in which they are 

 imbedded. The average diameters of the cells in both locali- 

 ties and their nuclei are, respectively, 55 ^ and 20 ^. The 

 cell membrane is in all forms quite distinct. The cytoplasma 

 in the cells of the oral sucker is made up of a fine reticulum, 

 definitely visible only with high powers, in the meshes of which 

 no formed elements can be detected ; and its staining power is 

 very feeble, possessing in cochineal preparations a colorless 

 appearance, while the muscular fibres and the cells lining the 

 excretory vessels of the sucker take a deep tint. The cyto- 

 plasma in the cells of the caudal sucker is likewise unstainable, 

 but very coarsely meshed, and present here and there cavities of 

 considerable size, sometimes comparable in this respect to the 

 central cavity of the renal cells in Sphyranura ; but these are 

 by no means regularly placed. Sometimes, also, one can find 

 here the radiate arrangement of cytoplasmic trabeculae so com- 

 mon in the renal cells. The nucleus of the cells in the sucker is 

 spherical, with a fine caryoplasma and one or more chromatin 

 nucleolar spherules ; while the nuclei of the caudal cells are often 

 collapsed to the size of the chromatin body which each may 

 contain. In cells possessing nuclei of the latter description the 

 cytoplasmic reticulum is very coarse, somewhat hyaline, and its 

 meshes are completely free from any formed element. It is in 

 such cells as these that are found an almost complete resem- 

 blance to the renal cells in Sphyranura. 



In Amphistomum the oral and caudal suckers, especially the 

 latter, are richly supplied with excretory vessels of varying 

 diameters. We could not determine whether these are con- 

 nected with the large cells of the oral sucker, because the num- 

 ber of the latter is very limited, and thus a favorable chance of 

 determining their relations to the vessels did not occur. In the 

 caudal sucker, however, in two or three cases, the membrane of 

 one of the finer excretory vessels was seen to be continuous with 



