ZooL.— Vol. II.] EISEN—OLIGOCHMTA. 2gl 



in size and shape, but the central core in the cytoplasm is 

 always rounded or ovoid. The cytoplasm of the core (fig. 

 113) is always coarsely vacuoled or foam-like, while that 

 outside of the core is much more finely granulated. The 

 distinction between the two is always great and well marked, 

 the central core staining paler than the surrounding cyto- 

 plasm. The best differentiation was effected with eosin 

 and thionin. With h^ematoxylin the foamy structure of the 

 cytoplasm becomes clouded and indistinct. 



These light-cells were not found outside of the prosto- 

 mium. There were none in the brain or in other ganglia. 

 Beddard described in Microdrilus salients a zone of clear 

 cells in the pharynx, similar to the corresponding zone in 

 Benhamia, and he calls attention to the astonishing resem- 

 blance between these two genera in this respect. In Dicho- 

 gaster such a zone exists in the two circular lips or ridges 

 of the mouth, next to the prostomium, but it is less well 

 defined than in Benhamia, common supporting cells appear- 

 ing between the clear cells. At one end of this zone there 

 is an area consisting of glandular cells. In the central 

 median line of each somite there is a continuous row of 

 glandular cells, six to ten cells deep, staining more intensely 

 than the regular goblet cells of the epidermis. In the center 

 are a few sense-cells, but as far as I can see with no sense- 

 hairs. This zone resembles the sense-zone found in the 

 equator of the somites of Benha^nia, but it is less differen- 

 tiated and defined. 



Mucocytes. — (fig. 12.) There are several kinds of lympho- 

 cytes in the coelomic cavity. The large majority consist of 

 very large mucocytes, each with a nearly central nucleus 

 and foam-like cytoplasm, radiating towards the nucleus. 

 These call for no special description. 



Morocytes. — This name is proposed for a certain kind of 

 lymphocyte with peculiar characteristics. The nucleus is 

 nearly always situated close to the cell-wall. The cyto- 

 plasm is separated into two distinct parts. One of these is 

 central, extending from one end of the cell to the other; 



( 10 ) December 23, 1899. 



