* 

 1 8 INEZ WHIPPLE WILDER. 



water when not swimming, instead of lying on one side as do the 

 newly hatched larvae of most amphibians. Nevertheless they 

 will not remain in the water, but persistently crawl out and lie, 

 often in a mass together, in the moist debris along the edges. 

 It is not until all external evidence of the yolk mass has dis- 

 appeared that they will remain in the water. 



The period of incubation in both of these broods was approxi- 

 mately eight weeks (53-55 days in the first case, and 56-57 days 

 in the second), a considerably longer time than that previously 

 estimated by me, which was five weeks. The terraria were kept 

 in a cool basement room, where the temperature did not vary 

 much from 21 C. (70 F.), which was probably somewhat above 

 the average temperature to which the eggs would have been 

 subjected under natural conditions along the banks of brooks in 

 shaded ravines. The former estimate of five weeks was based 

 upon observations of a batch of eggs which were deposited and 

 developed under still warmer laboratory conditions. As the 

 measurements and descriptions of an embryo from this batch 

 after 30 days' development (H. H. Wilder, '99) show a consider- 

 ably larger size and a more advanced stage of development than 

 the 34 day embryos of the batch of eggs here reported, one is 

 justified in the conclusion that at the higher temperature develop- 

 ment took place more rapidly. On the other hand, it is conceiv- 

 able that in nature the period of incubation might easily be 

 prolonged to more than eight weeks by the lower temperature 

 to which the eggs would certainly be subjected in the neighbor- 

 hood of cold, spring-fed, mountain brooks. Thus the batch of 

 eggs previously described by me as having been found in nature 

 hatching on September 24 (I. W. Wilder, '13), after an unusually 

 cool summer, may even have been deposited as early as the middle 

 of July, the month reported by Reed and Wright ('09) as the 

 month of maximum egg-laying for the species. This longer 

 estimate of the period of incubation under natural conditions 

 would account for the usual absence of the larvae of this species 

 from the brooks during the summer months, a fact which is 

 reported by my colleague, Mr. E. R. Dunn, in an article now in 

 press. 



The female which acted as the foster mother in the case here 



