678 HENRY H. DONALDSON 
points. Thus the percentage gains are 15.4 per cent, 11.4 per 
cent and 12.4 per cent respectively. This indicates that the frogs 
from the several localities change not only in the same manner, 
but also to about the same extent. 
28, VALUE OF C. GHARIS 
BRANDYWINE 
FEB. MAR. APR. MAY. JUNE. JULY. AUG SEPT. OCT. NOV. DEC. JAN. 
Chart 3 Based on data in table 7. 
When we take the mean of the percentages given above, we 
find it to be 13.1 per cent, the true maximum in all cases falling 
in July. This result can be controlled by another treatment of 
the data. 
TABLE 7 
Data on frogs from the Brandywine, 1909 
| 
NUMBER OF VALUE OF C 
| 
| 
| 
| 
| 
SPECIMENS 
Saas | ee ie DATE 
| Probable 
M. 1 Oe eal | Mean error of Range 
| mean* 
= = = £ = 
| 1909 | 
Moke eee aes > |) Hebruarey § tape 23-7 | 0220 | 20.925 1) 
Ds sentria | 6 | 5 | February 22 | 23.8 | +0.36 (21.7-26.8) 
30 | 7 | 4 | Mareh 3) | «624.0 | +£0.29 | (20.9=26:)) 
4.. LI eo Apr Sen | 24.8) | 20120 (23.2-26.3) 
ERWrarses e 6 | May 20 | 26.8 | +0.61 | (22.5-31.7) 
6 Penne 2 | June 19 26.3 | 0.30 | (24.4-28.9) 
7 .| a | | | 
our |) 3.) 25 1 Apustoe e138 26.1 | +0.24 (A=27 41) 
9.. | 5 °| | September 8 | 27.2 | +031 | 425.2-20.6) 
10ers Were 6 September 24 25.2 | £0.57 | (21.6-29.6) 
Wie ame 7 | October 19 24.5 | +0.43 | (20.2-28.7) 
IDs. 2 3 November 16 23.9 
=0.16 | (22.7-26.0) 
*See comments on pp. 671-672. 
