CHANGES IN WEIGHT OF CENTRAL NERVOUS SYSTEM 675 
of C in the former, but the discussion of this point will be deferred 
until the observations on the next lot of frogs have been presented. 
The probable error of the mean values of C given in table 5 
is open to the same interpretation as was given in the case of the 
Chicago frogs (see pp. 671-672). 
We conclude from this study of the Minnesota frogs that the 
relative weight of the central nervous system is low in the spring, 
high in the midsummer and low again in the autumn, and these 
relations are shown on chart 2. 
327 VALUE OF C. CHART 2 
MINNEAPOLIS 
FEB, MAR. APR. MAY. JUNE. JULY AUG. SEPT. OCT. NOV. DEC. JAN. 
Chart 2. Based on data in table 5. 
Observations on the frogs from the Brandywine, 1909 
These frogs were brought from the Brandywine Creek near 
Philadelphia, and in some ways represent the best of the three 
lots. The plan was to examine about twelve specimens at inter- 
vals of a month or less between the appearance of the frogs in the 
spring and their disappearance in the autumn. The two Feb- 
ruary series, as well as those of October and November, were 
taken within a spring house, and those of the intervening series 
from the neighborhood. The frogs did not emerge until the end 
of March. The July series was overheated in transport and could 
not be used. In all there are eleven series recorded. 
