« 
956 THE AMERICAN NATURALIST. [Vor. XXXIV. 
3. The measurements of Rana also show that there was no 
appreciable gain in the dry weight of the egg, with the albu- 
men removed, up to the time of hatching. There was during 
the same time a slight increase of water. Thus it appears 
that a part of the acceleration — by increased temperature — 
of the cell multiplications leading up to hatching may be due 
to the earlier inauguration of the imbibitory process. 
4. The developmental process up to the point where the 
water amounts to 75% of the whole weight is not retarded so 
much by lowered temperature as is the stage representing the 
maximum percentage of water (see Table IV). In the first 
stage assimilation of yolk and cell division is prominent; in 
the latter imbibition of water is the main process. The 
TABLE IV. — DESIGNED TO SHOW RELATIVE RETARDATION OF AN 
EARLY AND A LATER EVENT IN THE LARVAL DEVELOP- 
MENT, PRODUCED BY LOWER TEMPERATURES. 
1. TrmeE iN Days REQUIRED || 2. TIME IN DAYS REQUIRED 
TO ATTAIN Lae oF WATER; TO ATTAIN Maximum PER- 
i.e., 25% Dry SUBSTANCE. CENTAGE OF WATER. 
Highest | Medium | Lowest || Highest | Medium | Lowest 
Temper- | Temper- | Temper- || Temper- | Temper- | Temper- 
ature. ature. ature. ature. ature. ature. 
Rok o o a eh. 2 L^. 20 5 28 50 + 
Amblystoma....... 9 12 27 21 S t or 
Polo: o 220.25 XN $5 7.5 — 14 3% d 
Avere. 7. X 5.5 8.4 23.5 13.3 366 | 60+! 
Retardation in days, 
reckoned from time 
i : — 2.9 18 — 23.3 | 466 + 
required by highest 
temperature J 
. . ENRETE TEPU 1 
Retardation in per cent — 53% 327% en 175% | 350% 
1 This result is certainly too small, since the length of time consumed in my 
observations did not suffice to reach the minimum percentage of dry substance in 
the lowest temperature conditions. 
