242 University of California Publications. [zoologv 



Zellen erhalten bleiben und Driisensecret secerairen (Schleim- 

 drtisen), und andere, deren Protoplasma sich in feinkorniges 

 Driisensecret metamorphosirt wobei die Zellen vollkommen auf- 

 gebracht werden, zu Grande gehen, so dasz man ihre in Zerfall 

 begriffenen Kernen in Driisensecret finden kann (Korner-oder 

 Giftdriisen)." Nicoglu ('93), p. 447, finds that the cells of the 

 poison glands " wenn. ihre Stunde gekommen ist, wandeln sie sich 

 in toto in Secretmasse am." But up to this time they acl as 

 other gland cells in elaborating and retaining' a secretion in their 

 interior, as the pancreas cells do zymogen grannies. Schultz 

 ('89) does not think that all the cells of a gland are destroyed at 

 tin- same time, but such as do form a part of the secretion mass 

 must be regenerated; indicating that they are destroyed in the 

 process of secretion. Drasch ('94) merely states that the poison 

 glands of the salamander, if completely emptied, pass entirely 

 away, and are replaced by new glands. Observations of the 

 glands at various times after emptying show regressive changes 

 in all the layers. Vollmer ('93) also has described the process 

 of solution of the Leydig cells after strong electrical stimulation 

 of the glands, and has made careful statements regarding the 

 appearance of the emptied glands. The conditions in Plethodon 

 almost duplicate those he has described. 



It seems pretty well founded, then, that the poison gland 

 cells pass bodily into the secretion mass. But a distinction 

 should be made here, as Nicoglu has done, between the secretion 

 mass as that thrown out, and the secretion material, which is 

 the formed substance in the cells. There is no evidence of the 

 disintegration and solution of cells in the full but not discharged 

 gland. It is only when for some reason the glands are emptied 

 that the degenerative processes are discerned. Otherwise the 

 formed secretion is retained within the cells, which remain in a 

 normal condition at such times. 



This review of the literature describes very well the processes 

 which go on in Plethodon; PI. XXI, .Fig. 17, will show the 

 appearance of a gland on the day it was emptied. It has 

 shrunkeu greatly in size; as compared with others of the same 

 animal which, for some reason were not emptied, from three 

 hundred microns in diameter, say to one hundred microns. The 



