CHANGES IN WEIGHT OF CENTRAL NERVOUS SYSTEM 687 
When this formula is applied to the foregoing data, we obtain 
for the given total lengths the body weights which are entered in 
table 13. The results show that for the years taken, the body 
weight approximately doubles during each active season. This 
completes the first instance. 
The second instance is from Fischer-Sigwart (’97) who reports 
for R. temporaria the following body lengths at different ages: 
see ‘body length’ in table 14. 
TABLE 14 
R. temporaria 
CALCULATED 
AGES BODY LENGTH = =n 
Total length Body weight 
mm. gms. 
End of first year........ 20-25 | 68 0.8 
End of second year..... | 30-35 95 | 3.5 
End of third year....... (42-47) * | (128)* 8 .0* 
0 
End of fourth year... .. 55-60 163 | 22) 
*Interpolated by H. H. D. 
According to Boycott (04) the body length in R. temporaria 
is 36.6 per cent-of the total length. 
If now we take for the determination of the total iengths the 
highest values for the body lengths as given in the foregoing table, 
we obtain the series of figures marked ‘total length’ in table 14. 
Using the data on body weight given for R. temporaria by Boy- 
cott (’04) in his table (p. 375) we obtain the approximations for 
the body weights which are given in the last column of table 14. 
Here again the body weights are more than doubled from season 
to season during the last three years. The value of the foregoing 
calculations lies not in the exact numbers obtained, for these are 
in a measure open to correction, but in the indication which these 
numbers give of the rate of growth from year to year. 
tions on the Brandywine frogs however show fora given body weight, total lengths 
about 4 per cent less than those determined by the formula. These last frogs are 
therefore heavier for a given total length or shorter for a given body weight than 
those on which the formula is based. The formula does not apply to frogs less 
than 3.5 gms. in body weight. 
