394 MARGARET LEWIS NICKERSON. [Vol. XVII. 



they were certainly stained red, but at other times the question 

 of their color could not be decided. 



The cytoplasm of the cells containing the sacks shows a 

 variety of conditions, corresponding, I believe, with the stage 

 of activity. Those cells in which the intracellular canals are 

 large, and the surrounding radial zones narrow, show a coarse 

 condition of the cytoplasmic reticulum, which stains green, while 

 cells containing small intracellular sacks, with a broad surround- 

 ing zone of radial filaments, possess a much finer structure and 

 show the presence of abundant red granules. The latter con- 

 dition is, I believe, a young stage in the activity of the cell, the 

 former an advanced stage. 



The several canals leading from the intracellular sacks and 

 the common duct resulting from their union are stained deep 

 red with the Biondi-Ehrlich mixture and are seen to be en- 

 veloped in a sheath which also takes the red color. This 

 sheath, which is directly continuous with the radial vesicle sur- 

 rounding the intracellular sack, envelops each small canal from 

 its point of union with the terminal sack and beyond the junc- 

 tion of the several canals forms a common sheath for the main 

 duct. The sheath widens considerably near the mouth of the 

 main duct, while the duct itself close to the exterior often shows 

 a contracted lumen. Although no mention of the sheath was 

 made in the first part of this paper, a reexamination of the 

 Vom Rath preparations shows that it is always present, but, 

 owing to the lack of a differential stain, is difficult to see except 

 with the highest powers. 



By the side of the main duct, close to the point of junction 

 of its branches, is situated a large nucleus within the sheath. 

 The sheath broadens markedly where it encloses this nucleus. 

 The nucleus is surrounded by a very clear, transparent, sharply 

 limited area, which probably represents a vacuole. This nucleus 

 within the sheath of the main duct is, I believe, always present, 

 but may of course lie outside the section which contains the 

 duct ; for this reason it was not noted in the sections studied 

 and drawn for this paper. 



University of Minnesota, Minneapolis, 

 January, 1900. 



