620 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Anterior Genital Mass. 



The anterior genital mass consists, as already mentioned, of the mu- 

 cous gland, the nidamental gland, and the prostate gland. The first two 

 unite to form a simple, conspicuous mass, each gland consisting of a 

 number of foldings of a greatly thickened epithelium. After fixation in 

 Miiller's fluid, it is not easy to distinguish between these two glands, as 

 their tubules have no constant position or shape ; but after fijcation in 

 Hermann's fluid the resulting difi"erentiation of the contents of the 

 cells enables one to recognize at a glance the difference between the 

 mucous and the nidamental regions. The actual space occupied by 

 the mucous tubules is about one third as great as that occupied by the 

 nidamental tubules, and the former are found mostly on the back and 

 left sides, although a few extend into the center of the anterior genital 

 mass and are there surrounded by the nidamental tubules. The out- 

 line of these combined glands is not regular, because some of the nida- 

 mental tubules project into the liver. 



The nidamental cells are light colored after fixation in Hermann's 

 fluid, the cell walls and nuclei being the only parts stained. In the 

 animal thus fixed, the cells were congested, almost obliterating the 

 lumen of the tubule, while in the one prepared in Miiller's fluid and 

 stained in iron haematoxylin the cytoplasm was faintly tinted and the 

 cells shrunken so as to leave a large lumen. The mucous-gland cells 

 which were fixed in Hermann's fluid were stained a deep brown, this 

 color being due to the presence of numerous spherical bodies which 

 fill the cell. This is the differential reaction which enables one to 

 distinguish between these two glands. An animal that had recently 

 discharged its mucous secretion was fixed in Miiller's fluid and stained 

 in haematoxylin followed by Bordeaux red. It showed the presence 

 of a few small bodies in the distal ends of the flask-shaped cells. The 

 large bodies took the haematoxylin stain in the center and the Bor 

 deaux red around their periphery, while the small ones, just forming 

 in the cytoplasm, took an exclusively Bordeaux red stain. It would 

 seem, then, as if this secretion of the mucous cells was not a chemi- 

 cally homogeneous substance. 



The prostate gland of Polycerella zoohotryon (Figure 8, gl. prost.), 

 unlike that of Polycera (Pohl, : 05, p. 434), is not folded, but consists 

 of a large flask-like sac, the fundus of the flask being on the left side 

 of the body, and its neck continuous with the prostate duct. The 

 histology of this gland presents the following points of interest. The 

 cells composing the main lining of the gland are elongated and mutu- 

 ally flattened ; the nucleus is prominent, the cytoplasm finely and uni- 



