The Wood-frog, Ranu sylvatica LeConte. 97 



Mouth-parts (Plate vm, Fig. 5.) : The upper lip has tin: customary 

 fringe of teeth on the boundary. Beneath this, on either side, are two 

 rows, the first being more lateral to the mandible than in the other four 

 species of Rana. The lower lip contains four labial rows, which are 

 more wavy than in the other four species of Rana. In 44 specimens, 

 eight were found with 3 lateral rows on each side of the upper lip, i. c., 

 three besides the upper lip fringe ; in three or four instances there were 

 three lateral rows on one side, and in one instance one of these was 

 subdivided. In the lower lip the fourth row is rarely absent ; the second 

 is sometimes discontinuous in the middle, the first discontinuous in one- 

 half of the specimens. 



THE LARVAL PERIOD. 



The development period lasts about 90 days. In 1906 the first eggs 

 were laid April 16; 93 days later (July 8) our first transformed examples 

 were noted. Eggs laid March 29, 1907, in three different ponds, de- 

 veloped and larvai transformed in 91 days in a shallow transient pond 

 (dried up June 28) ; in 97 days in another exposed pond (dried up the 

 last of August); in 115 days in a deep, heavily-shaded, spring-fed, per- 

 manent pond. The true larval periods were, in these three instances, 

 67, 73, and 85 days respectively. In 1908 the periods from eggs to 

 transformation were 96 days (73 days of larval life) and 95 days (74 

 days of larval life). In 1911, in one pond, only 61 days intervened 

 between eggs and transformation, 44 days of larval life; in a second 

 pond, the interval was 75 days or 62 days as larva?; in a third, 78 days 

 or 62 larval days. As larvse, the periods range from 44 to 85 days 

 with an average of 67 days; from eggs to transformation the periods 

 are 61 to 115 days, the average being 89. 



THE TRANSFORMATION. 



Transformation begins about the first day of July. In 1906 the first 

 record was July 8; in 1907, June 28. The first record for 1906 (July 8) 

 was for a spring-fed, permanent, deep pond, where this species in 1907 

 did not begin to transform until July 22, and this lasted until August 1. 

 In 1907, in another pond, transformation began June 28 and the 

 species was recorded as transforming there for a period of 11 days. 

 In 1908 the species began to transform July 6 in two ponds, and so 

 continued until July 21. In 1911 we have our earliest record of trans- 

 formation, namely, June 8. An interval of 19 days elapsed before the 

 species began transformation in the other ponds. Thus we see that 

 transformation may begin as early as June 8 or extend to August 1. 

 An average of first dates for several years gives June 27, or approxi- 

 mately July 1. 



The size at transformation of 139 specimens varies from 12 to 21 mm., 

 rarely over 19 mm. ; the average is 16 mm., the mode is 18 mm. (Plate 

 x, Fig. 4.) 



