240 University of Calif orwia Publications. izoolog? 



in this respect the poison ami mucous glands; the latter have 

 capacious lumens (PI. XX, Fig. 2), often filled with a clear 

 secretion. The large glaud cells each have a number of nuclei 

 (Nieoglu '9-'!; Drasch '92), not over four in Plethodon. They 

 are round or oval, of regular outline, and lie normally upon or 

 very near the wall of the gland, and so at the base of the cells. 

 The internal structure of the nuclei is simple. There is a scanty 

 net work and few chromatin granules; usually also one or two 

 nucleoli. 



The cells and nuclei of the small or mucous glands are distinct 

 in every way from those of the poison glands. The cells are low 

 and cubical and show a filar structure (pseudo-filar, Nieoglu '93) . 

 This is seen in sections stained either with Van Gieson, Mallory 

 or iron haematoxylin. The nuclei are smaller than those of the 

 poison glands, and angular instead of regular in outline. They 

 invariably stain intensely black in iron haematoxylin, remaining 

 so when the nuclei of the giant cells have decolorized to a very- 

 faint gray (PI. XX, Figs. 2, 3; PL XXII, Figs. 18, 19, 20). 



A general comparison of the two sorts of glands might be 

 instituted in some such terms as these. The poison glands are 

 very much larger than the mucous glands, and have contractile 

 walls; the mucous glands lack this character. The extreme 

 dimensions of the former on the tail are approximately from 1400 

 microns in length and 380 microns in breadth to 680 microns in 

 length by 200 microns in breadth, and half the latter figures on 

 the body. The mucus glands vary from 93 by 90 microns on the 

 tail to 60 by 40 microns on the body. This alone, without 

 closer inspection, would serve to generally distinguish the two 

 varieties of glands; but in addition the poison glands have no 

 lumina, the cells and nuclei are much larger than in the other 

 glands (mucous average about 11 microns in greatest diameter, 

 poison about 20 microns) and stain differently; and above all 

 the character of the secretion is vastly different. 



As might be gathered from the name often applied to them, 

 the secretion in the poison glands is composed of granules. 

 These are of varying size, and the cells are entirely filled with 

 them. The mass stains from red (PI. XXIII, Fig. 31, sec.) or 

 reddish yellow to a dark purple in Mallory; in Van Gieson the 



