1925] 
St over: A Synopsis of the Amphibia of California 
255 
60° to 65° F. began hatching on the twelfth day, and the greater part 
of the larvae were out on the thirteenth day. 
Freshly hatched larvae measure as follows: total length, 7.3 to 
7.7 mm. ; tip of snout to gills, 1.47 mm. ; height of fin over all at the 
anus 1.87 mm. In the field the young, upon emerging from the jelly 
mass, are found clinging to or lying upon the latter in the first few 
days after hatching. 
Subsequent to hatching, the tadpoles of Rana boylii boylii experi- 
ence a fairly rapid growth, considering the nature of their habitat. 
From three to four months seems to be required for the growth 
between hatching and metamorphosis. 
The earliest record of transformation is from a creek at Lafayette, 
Contra Costa County, where larvae undergoing metamorphosis were 
found on July 18, 1922. At the immediate locality of capture of the 
specimens this creek is in the bottom of a gulch about 20 feet in 
depth. The concentration of heat due to the protected location of this 
particular part of the creek may have been responsible for the early 
arrival at metamorphosis. The same year (1922) in an adjacent 
stream (San Pablo Creek) eggs were found on April 20, 1923, and 
by August 7, the greater part of the boylii population there had 
already metamorphosed. Transformed young frogs were found in 
Pine Canon, near Mount Diablo, July 22, 1912. Larvae of Rana 
boylii boylii seen in a creek at Manor, Marin County, on July 6, 1919, 
measured 40 millimeters or less in total length, and hind limbs were 
developed on some individuals. Two larvae from near Vacaville, 
Solano County, collected July 3, 1912, are 28 millimeters in total 
length. In Papermill Creek, where eggs were found in abundance 
on May 5, 1923, I found, on July 8, 1922, only scattered larvae of 
small size. In 1922, it was not until August 26 that the larvae in this 
creek were undergoing metamorphosis. 
The larvae of Rana boylii boylii gain hind limb buds when about 
30 millimeters in total length. At metamorphosis the younger frogs 
of this species are comparatively large (pi. 16, fig. 49). Several 
specimens acually undergoing the transformation, which were col- 
lected in San Pablo Creek on August 7, 1922, measured 22.0 to 23.6 
millimeters in head-and-body length and one was 26 millimeters long. 
Several fully metamorphosed young frogs collected at the same time 
ranged from 23.2 to 30 millimeters in head-and-body length. The 
young frogs seem to make very little progress in growth during the 
winter season following their metamorphosis. Young animals col- 
