No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 483 



cell. The cell has thus no external openings and no ducts or 

 fibers which penetrate into the enveloping tissues. 



19. Subcutical Gland Cells of Piscicola rapax (Verr.). 

 (Plate 25 ; Plate 26, Figs. 198-203.) 



(These cells lie for the most part in the body cavity, between 

 the body muscular wall and the intestine. Two modifications 

 of them may be distinguished : (i) those at the ends of the 

 body, near the suckers and in the wall of the latter, which are 

 comparatively small, and the relatively short cell ducts of which 

 open at all points of the surface of the body at the ends of the 

 body and on the inner surface of the suckers ; these seem to 

 resemble the second modification in all respects except size ; (2) 

 the larger type of these gland cells, which I have studied exclu- 

 sively, are massed together in that portion of the body cavity 

 which extends from the region a little anterior to the brain, 

 nearly to the posterior end of the body, the greater number of 

 them being in contact with the inner surface of the body 

 wall.) 



In order to find all the functional stages of these cells one 

 must study preparations of worms of various dimensions, since 

 all the stages cannot be found in a single individual ; I made 

 consecutive series of sections of seven different individuals, the 

 smallest being about 6 mm. in length, and the largest being fully 

 matured. The remarkable cycles of the nuclear and cell stages, 

 to be described below, were equally well discernible with all 

 three of the fixatives employed, namely, Flemming's fluid and 

 alcoholic and aqueous solutions of corrosive sublimate ; various 

 double stains were used. 



These cells, when they reach their fullest dimensions, are so 

 enormous that they may be readily seen with the naked eye. 

 Their single ducts all open on the surface of the body, between 

 the epithelial cells, a little anterior to the region of the sexual 

 pore ; their openings are at this point equally numerous on 

 the dorsal, lateral, and ventral sides of the worm. The most 

 posterior gland cells of the body send their ducts a distance of 

 four-fifths the total length of the body before they open on the 



