2'A University of California Publications. [zoology 



SUMMARY. 



1. The skin glands of Plethodon oregonensis, as of most 

 Amphibia, are of two kinds: granular and mucous. The two are 

 distinguished by the character and staining reaction of their 

 secretions, and by other histological features, as well as by the 

 sizes of the glands. 



2. The bodies of the large glands possess an investing mus- 

 culature, and in addition the duets have both dilator and con- 

 strictor muscles lying in the epidermis. 



3. The granule glands are poison in character. 



-I. In the elaboration and ejaculation of the secretion the 

 poison glands are destroyed. 



5. Renewal takes place by the growth into all the old glands 

 of a new and smaller gland, which is mucous in character. The 

 presence of this smaller sac is not dependent upon the removal 

 of the secretion of the large glands, for whether this occurs or 

 not, the fundament giving the mucous reaction is found in all 

 glands; in those which show no degeneration as well as in those 

 where it is wide-spread. 



6. The growth of the new gland is dependent upon the 

 removal of the secretion about it. There is evidence that even 

 in case the glands are hindered in their development, they still 

 secrete mucus. But when not hemmed in by the heavy granular 

 contents of the large glands they grow and take the place and 

 very probably assume the function of the old glands which they 

 replace. 



7. Both musculature and epithelium of the granule glands 

 have a direct nerve supply. The gland cells are surrounded by a 

 basket work of fibres, which in some cases have terminal expan- 

 sions lying on the nuclei. The muscles are supplied by nerves 

 with typical endings of expansions or bulbs, as well as by fine 

 twi^s without terminal expansions. 



Zoological Laboratory, 



University of California, 

 April 39, 1904. 



