226 University of California Publications in Zoology [Vol. 27 
1.6 millimeters. Melanophores are scattered over much of the general 
body surface. The general coloration beneath the pigment is yellow. 
For a few days after hatching the larvae are rather quiet but soon 
thereafter they begin feeding ; growth is then quite rapid, the typical 
blunt compressed body form of the tadpole being assumed within ten 
days. At the Thornhill pond it was noticed that the Hyla larvae were 
very active and swam up near the surface of the water on bright 
warm days, whereas in cold, cloudy or rainy weather most of them 
stayed down, near the bottom of the pond and w T ere relatively inactive. 
A close check on the subsequent growth of the Ilyla larva is 
difficult under field conditions because egg laying continues over a 
long period. At the Thornhill pond in 1922 the first metamorphosed 
hylas were noted on May 9. The first eggs in that year were deposited 
about February 10, so that the egg and larval stages probably involved 
a period of 88 days. This is more than the time required for Hyla 
versicolor at Ithaca (Wright, 1914, p. 51) and, I believe, is probably 
longer than is required for Hyla regilla in localities in interior Cali- 
fornia. The Thornhill pond is shaded on the south by a grove of tall 
Monterey cypresses and other trees, and the locality is often reached 
by the ocean fogs which cover the San Francisco Bay region, so that 
the heat quotient of the pond is below that of many of the pools in 
the warmer parts of the State. 
The size attained by this hyla in its larval stage is somewhat 
variable, depending probably upon the amount of food available, the 
date upon which egg deposition occurs, and the water temperatures 
prevailing during larval life. The largest tadpole at hand measures 
45 millimeters in total length. One larva only 28 millimeters long 
has the hind limbs well developed, while another of 40 millimeters 
has only small limb buds. At metamorphosis the head-and-body 
length varies from 11.2 to 16.5 millimeters. The foregoing measure- 
ments are of specimens obtained at Thornhill pond and at Lafayette. 
Transformation, like egg deposition, occurs over a long season. 
In 1922 the first metamorphosed hylas at Thornhill pond were found 
on May 9, they were out in numbers on June 2, but as late as August 10 
individuals still in process of change were seen there. 
The following is a list of recently metamorphosed specimens of 
Hyla regilla from California ; it serves to indicate the general seasonal 
program of the species in different parts of its range. 
