24(i University of California Publications. [zoolorv 



glands stained in iron haematoxylin with the other mucous glands 

 is just as complete (compare PI. XX, Figs. 2 and 3). 



There can be nothing clearer than the reaction of the new- 

 glands to Mallory's stain. The blue color is present in every case 

 as shown by a study of hundreds of glands. In the very large 

 glands on the back of the tail the ingrowing glands never reach be- 

 yond a certain size, such as is shown in PI. XXIII, Fig. 31. This 

 may possibly be due to some effect of the poison which would 

 hinder the growth of the small gland, or, as seems more likely, 

 the new gland does not develop because it is hemmed in and 

 hindered in its growth by the pressure of the large amount of 

 secretion in the old gland. Drasch ('94) has made this sugges- 

 tion previously, but does not say where the replacement glands 

 are located. But in all the small poison glands which lie along 

 the sides of the tail and also on the dorsal and ventral surfaces, 

 particularly in the constriction, can be seen all stages of devel- 

 opment of the mucous glands within them, from the small buds to 

 new glands which have almost entirely replaced the old ones. 

 The small poison glands differ from the largest ones in no other 

 respect than in size, and for that reason it seems fair to conclude 

 that the processes of regeneration going on in them are charac- 

 teristic, and typical of those believed to occur under certain 

 circumstances in the large glands of Plethodon, and as observed 

 in other salamanders. There are many cases to be seen in 

 Plethodon in which some glands are so far replaced by a new 

 mucous gland that only a faint crescent of granular secretion can 

 be seen, the rest of the contents being mucus. In other cases 

 the amount of granular material is a little greater, and in still 

 others we may see the gland half granular and half mucus 

 (PI. XX, Fig. 3; PI. XXII, Figs. 18, 1!), 20). In all these the 

 granular portions stain as do the same parts of the large glands, 

 while the remainder reacts to Mallory and the other stains as do 

 the small sacs in the large glands and the mucous glands outside 

 of these. 



To sum up the foregoing we may say that the small glands 

 within the large ones react like known mucous glands to Mallory's 

 stain and mucicarmine, and in the same way so far as the nuclei 

 of the replacement and mucous glands of the tail are concerned, 



