vol. i.i Hubbard. — Protective Devices in Salamanders. 159 



the daytime. Though conspicuous, it remains quiet when dis- 

 covered under boards or rotting logs, not writhing or jumping 

 about as Batraehoseps frequently does. Several times at night 

 individuals in the terrarium were found alert and walking about, 

 but the approach of the light soon sent them back to their hiding 

 places beneath the bark and stones. 



As stated before, this work began with the study of the tail 

 of Plethodon oregonensis. This member in the great majority of 

 cases is enlarged, the swelling being marked off from the rest of 

 the body by a constriction just behind the anus. Out of sixteen 

 individuals direct from the field fourteen were distinguished in 

 this way, one of the exceptions being an immature individual, 

 the other full grown. Of sixteen museum specimens fifteen 

 showed the tail enlarged to a greater or less extent. The extreme 

 of the swollen as compared with the unswollen condition is weH 

 shown in fig. 1. PI. XVI. The tail segment in which the condi- 

 tion occurs is shorter than those immediately preceding and 

 succeeding, as can be seen in figs. 1 and 2. This enlargement is 

 independent of sex, for it is found in both male and female, in 

 sexually immature specimens, and at any time of the year, 

 regardless of the breeding season, which, as recorded by Dr. Van 

 Den burgh, occurs in April. Thus I have noted it in specimens 

 taken on the following dates. February 28, March 17, March 31 

 (sexually immature), April 17, August 20, October 1 and Novem- 

 ber 30, and its absence in two specimens taken March 17 and 

 April 17. 



At least some others of the urodela show a condition of the 

 tail similar to that of Plethodon. In the collection at the Cali- 

 fornia Academy of Sciences it was present in Plethodon croceater 

 and in Amblystonia opacum. The former species oecui-s in Cali- 

 fornia, the latter east of the Mississippi, from Massachusetts to 

 Louisiana, so the peculiarity is not a matter of geographic ranee. 



An examination of the tail, both macroscopic and microscopic, 

 reveals the anatomical nature of the swelling. The dorsal half 

 of the epidermis of this organ is covered with minute and thickly 

 crowded pores which can be seen with the naked eye. These 

 are present alike in tails enlarged and in those that are not, as 

 shown in fig. 1. The skin of this region is enormously thickened. 



