CHANGES IN WEIGHT OF CENTRAL NERVOUS SYSTEM 689 
C is not 20.2 but 22.8, as observed. When this latter value of C 
is taken, then the weight of the central nervous system at the mid 
season becomes 0.0941 gms., which is nearly the weight found 
at the end of the season. This value is entered in table 15 under 
Cz=22 8. 
The first comment on these results is that they are in good 
agreement with the direct observations on the weight of the cen- 
tral nervous system in R. temporaria (Donaldson, ’08, table 9), 
and may therefore be used as a basis for further argument. 
The foregoing computations have been repeated in the case of 
the data for R. aurora, (table 13), but as the results depend en- 
tirely on the fact that the frog more than doubles its body weight 
TABLE 15 
R. temporaria 
CALCULATED WEIGHT OF CENTRAL NERVOUS 
| SYSTEM 
TOTAL LENGTH BODY WHIGHT 
C=20.2 C=22.8 
mm. gms gms | gms 
128 | 8.0 0.0614 
150 15.0 | 0.0834 | 0.0941 
| 
| 
163 22.0 | 0.0968 
from season to season, and as we do not have data to control 
them, it does not appear necessary to put down the numerical 
findings. 
If now we attempt to picture how these growth changes which 
have been determined are related to one another in order to give 
the results found, the following appears. 
As shown in table 15, the weight of the central nervous system 
at emergence is .0614 gms. and at hibernation .0968 gms., a gain 
of 57 per cent. For the mid weight value in this table, or a body 
weight of 15.0 gms., the weight of the central nervous system 
would be .0834 if C remained constant. We know however that 
C rises in the first half of the season and in July is 13 per cent 
greater than in March. Taking C as 22.8 therefore, or 13 per 
cent more than its initial value, the weight of the central nervous 
system becomes .0941, or almost that found at the end of the 
