954 THE AMERICAN NATURALIST. [VoL. XXXIV. 
recorded for the highest temperature. Owing to great accel- 
eration and high rate of mortality, the first series (1; 3) 
was very short. To supplement this record I took some 
embryos of the same spawning, which had been for seven days 
in the aquarium, at a temperature of 12?—15? C., and placed 
them in the warm chamber (I; 4). 
.. An accident prevented my getting a record for Bufo at the 
lowest temperature (6°—8° C. 
Conclusions. — 1. All the processes involved in the early 
development of these larva are accelerated by an increase of 
TABLE III. — BUFO AMERICANUS. 
1. TEMPERATURE 12° 18° C. 
. Wt. 
DATE. No. of | Length. AUN apes : pese id PS c 
Days mm. T Substance. Water. s uc dt 
; mg. 
Apnis6..... — = -— — see 
May. 3... » 4.8 3.00 82 2.18 221 
Es 9 6 3.36 1.02 2.34 30 
We oe ak ae II 7.5 5.98 .98 5.00 16.3 
N^... 21 10.5 12.68 84 11.84 6.6 
a Us ris 24 10.5 II.00 70 10.30 6.4 
"o dE is 28 10.8 12.00 64 11.36 5.3 
uM Sere 32 10.5 12.08 51 11.57 4.2 
"c 3 rk. 35 10.5 11.62 60 11.02 5.1 
2. TEMPERATURE 22°-25° C 
Apiiab. s sas — — — — -— n 
ak 2d 4 5 2.50 .86 1.64 34-4 
Nay 3. 5. 6 8 4-40 -94 3.46 21.4 
reek ok 7 IO 9.54 1.10 8.44 11.5 
Ade ru rem 9 II 15.96 1.00 14.96 6.6 
ai, oq 11 13 21.00 .96 20.04 4.6 
"o E us 13 13 21.44 .92 20.52 43 
Se AQ oes 14 13 22.12 -90 21.32 4 
a er uu po 21 13 20.82 I.OI 19.81 48 
temperature within the limits used: + 6? to + 25? C. This 
is true of the early cell divisions preliminary to hatching, as 
