686 HENRY H. DONALDSON 
TABLE 12 
Average values of the percentages of water in the brain and spinal cord of the several 
lots of frogs, from data in tables 1, 3 and 6 
BRAIN CORD 
Frogs trom Chicago- eye ace te | 84.6 80.4 
Hrogs trom Mannesota, 150.0240. ecee en |. 85.0 80.1 
Frogs from the Brandywine............... 84.6 80.0 
2. Changes in length 
On the growth of the frog in length during the active season 
only two sets of data have been found. In the first instance 
Miss Dickerson (’07) gives pictures of Rana aurora at one, two 
and three years. On measuring these, I obtained the body lengths 
given in table 13. 
Using the determinations made on R. pipiens—which Rana 
aurora resembles—and according to which the body length is 
37.5 per cent of the total length—we obtain the calculated total 
lengths given in table 13. 
From-a series of determinations of the relation of body weight 
to total length in R. pipiens, Dr. Hatai (’11) has developed the 
accompanying formula: 
y = 158 Log(@@ + 6.5) —63 
in which y is the total length in millimeters and x the body weight 
in grams. This expresses the normal relation of total length to 
body weight in R. pipiens’. 
TABLE 13 
Rana aurora 
CALCULATED 
AGE | BODY LENGTH mas =e See ee et 
Total length Body weights 
yrs. mm. mm. gms. 
| en Perey Ee Nees eee 36 | 96 3.6 
D te Shee Te eta Oe Tees 50 | 133 10.9 
DEO 
SM ee oe ey ly, > 63 | 168 
* This formula was based on themeasurements of several series of Chicago frogs, 
R. pipiens. It fits the observations on the Minnesota frogs also. The observa- 
