CHANGES IN WEIGHT OF CENTRAL NERVOUS SYSTEM 677 
Cord 
SERIES | WEIGHT LENGTH | PERCENTAGE OF WATER 
ble Asien bu, Gey Aes Le, Oe ee 0.0394 16. 2 79.9 
Ns 5 ee oe 0.0382 16.4 78.9 
St es Piece se 0.0354 14.8 | 79.4 
A a deo Ea Sale a | 0.0334 15.0 80.3 
ne eyes Meee oe Sok. eee 0.0429 16.5 80.4 
Ci ah es tres ek wees 0.0361 15.8 Till 
(AEROS A co. See eae 
Sipe meenipe yn Se a 0.0417 ee 80.9 
Oia ae eet ot ey ae 0.0497 AG 80.0 
Gee ey tee oe 0.0446 ee 80.4 
linen reeset Meo ccm St, 0.0392 16.3 80.7 
ae tae Rte erin: 0.0404 6.6 80.6 
When the values of C for these frogs are plotted as in chart 
3, we obtain a series of records which, although irregular for the 
midsummer season, fit very fairly with the entries in the two 
preceding charts. Asin the Chicago lot the average value of the 
probable error (table 7) is 0.3. The size of the error in this case 
is open to the same explanation as was given before in the cases 
of the Chicago and Minnesota lots. The diminution on the rela- 
tive weight of the central nervous system in the autumn is shown 
better in this series than in either of the two preceding. 
The data as they stand justify in this case the conclusion which 
has been drawn from the other two sets of data; namely, that the 
relative weight of the central nervous system is low in the spring, 
high in the midsummer and low again the autumn. It will be 
noticed that the absolute values for C are again different from those 
in the preceding cases, being the lowest of all. 
It is hard to compare the ranges of C on the charts 1, 2 and 3 
because of the difficulty of constructing satisfactory curves by 
which to make the comparison. I made for my own use however 
a series of curves, employing each to control and correct the others 
and obtained the following relations of C, always taking the late 
March value as the initial one. 
The Chicago frogs were found to range in the value of C from 
24.7—28.5 or 3.8 points, the Minnesota frogs from 28.1-31.3 or 
3.2 points, and the Brandywine frogs from 24.0 to 27.0 or 3.0 
