690 HENRY H. DONALDSON 
season. We conclude from this that the growth of the central 
nervous system is precocious and takes place mainly in the first 
half of the active season. 
The relations just described are plotted in chart 5. Here the 
shape of the curve for the increasing weight of the central ner- 
vous system is fixed for the last half of the season, but the form 
given to it for the first half is based on the assumption that 
growth must begin slowly and become rapid only later. 
Until direct observations on the body growth can be made for 
the exact control of this curve, the form given here may stand 
as a probable representation of what occurs. 
10 - WEIGHT IN GMS. CHART 5 10 
09 .09 
.08 .08 
GROWTH OF 
CENTRAL NERVOUS SYSTEM 
CALCULATED 07 
O07 
FEB. MAR APR. MAY. J " os 
; y é UNE. JULY. AUG. SEPT. OCCT. NOV. DEC. JAN. 
Chart 5 Curve for the growth of the central nervous system, R. temporaria. 
Based on data in table 15, using the value of C=20.2 for March and October and 
the value of C=22.8 for July. 
It is to be remembered however that this curve asit stands is 
based on observations on R. temporaria, but from what we know 
about this species it seems most probable that it applies to R. 
pipiens also. 
In connection with the phenomena just described, it may be 
well to review briefly the growth conditions for the frog at various 
seasons. When a normal frog disappears in hibernation, it 1s 
prepared for the experience. The digestive system has suffered 
involution and a considerable amount of fat has been stored in 
the fat bodies, liver and muscles. The frog emerges from hiber- 
nation with most of this stored material intact and lives on it 
largely during the breeding season and the earlier spring weeks. 
