The Pickerel-frog, Rana palustris LeConte. 67 



instances of 3 successive bunch.es upon one twig, and 7 instances of 2 

 bunches (Plate xv, Fig. 2). The greatest number of bunches on one 

 support was secured May 5, 1909, when 7 were noted. Quite frequently, 

 on one tuft of grass or stick, one finds a bunch or more of Amhy stoma 

 punctatum or Rana pipiens eggs with as many as two Rana palustris 

 complements immediately above them — seldom below, because laid 

 later. At the time of deposition a bunch may be 1 to 2 inches in diam- 

 eter, but it soon becomes 3|- to 4 inches. It is usually firm and globular 

 (Plate VI, Fig. 4). Frequently it has been observed that some of the 

 older egg-masses were quite frayed in appearance or scattered into 

 several smaller masses. By observing the frogs it became apparent 

 that this condition resulted from the nervous threshing of the females 

 in their successive attempts at taking a satisfactory position. Then, 

 too, Notophthalmus viridescens (the newt) often seizes an individual egg 

 for food and pulls until it disentangles it. The egg-complement of 

 Rana palustris may be from 2,000 to 3,000. 



The bright yellow vegetative and brown animal poles make the eggs 

 of R. palustris the most distinctive of all our Rana eggs. The outer 

 envelope ranges from 3.6 to 5 mm.; the average is 4.0 mm., the mode 

 4.0 mm. The middle envelope ranges from 2.4 to 2.8 mm. ; the average 

 is 2.6 mm., the mode 2.8 mm. The vitellus diameter is from 1.6 to 

 1.9 mm.; the average is 1.7 mm., the mode 1.6 mm. (Text-fig. 1b.) 



THE HATCHING PEEIOD. 



In nature the hatching may extend from 11 to 21 days. In 1906, 

 when the average maximum air- temperatures were 60 degrees, 21 days 

 were recorded for several bunches. In 1910 the same result was secured 

 when eggs laid early (April 6) hatched 21 days later (April 27) under an 

 average of 60 degrees maximum air-temperature. In 1907, of 69 

 bunches charted in 3 different ponds, 32 hatched in 14 days, 18 in 15 days, 

 19 in 16 days. In 1912 and 1911, several different bunches hatched in 

 11 days, the maximum air-averages being from 63 to 67 degrees. 



In the case of fresh eggs brought into the laboratory, 6 to 7 days 

 were required for hatching. About the same period was required for 

 eggs laid in laboratory by mated pairs. Of the water-temperatures, we 

 have too few to generalize with any degree of certainty. 



THE MATURE TADPOLE. 



Length of the body contained 1.4 to 1.9 times in the tail, average 

 1.6. Width of the body in its own length 1.4 to 1.85, average 1.6. 

 Nostrils nearer the eyes than the end of snout. Eye about equidistant 

 (sometimes nearer the snout) between spiracle and end of the snout. 

 Distance between nostrils 1.5 to 2.1 in interorbital space, average 1.8; 

 in mouth 0.9 to 1.8, average 1.2. Spiracle sinistral 1.2 to 1.9 times 



