Effects of External Conditions 137 
prepared (Table 11) which inciudes all the cases in which this 
point can be tested. 
TABLE 11 
Series of 1907-1908: percentages of increase* in the intervals between successive measurements 
6 WEEKS 2} MONTHS 7 MONTHS { 
ABSOLUTE MEASURE- | PERCENTAGES OF | PERCENTAGES OF 
MENTS INCREASE | INCREASE 
| . ; aa ae | : 
Weight Fal | Weight Tail Weight ea 
length length length 
SS 
ein { Warm.........| 12.997 | 68.83 | 32.1% | 12.5% | 32.7% | 11.5% 
tet | Cor a ee 13.123 54-16 | 40.2% | 16.9% | 25.1% 17.9% 
| | 
= $$$. 
Femal (Wits cease acl 12.282 | _ 69.06 28 .8% 10.3% 45-38% 14.2% 
poe \ Cold ae ee | 11.400 I “SEs91 | 33.1% | 16.0% | 48.4% | 25.7% 
**See foot note on p. 120 above. 
tIn considering the figures for 7 months, it must be recalled that only 13 males (7 warm 
+ 6 cold) have been kept till this time. In figuring percentages of increase for these males, 
therefore, the later figures have been compared with those for this same group of ‘mated 
males,” and not with those for the males in general. In the column for 24 months, on the 
contrary, the figures for “all males’ 
. 
are given. 
Under the “‘6 weeks” column, we have the absolute measure- 
ments of weight and tail length for males and females belonging 
to the warm room and cold room lots. In the column for 25 
months is given for each group the percentage of increase of each 
of these characters, during the interval between the two measure- 
ments. In the “7 months” column are given the percentages of 
increase over the measurements for 24 months. For each sex 
are presented two horizontal rows of figures: those for the “warm” 
and the “cold” lots respectively. It is thus easy to compare the 
contrasted figures for any one character. In each pair of these 
contrasted figures, that one has been printed in heavy type which 
represents the rate of increase for the group which had previously 
shown a Jower mean value for the character in question. ‘This 
group should, according to the hypothesis, be expected to have 
undergone a more rapid rate of increase. As a matter of fact, 
it will be noted that in 7 out of the 8 pairs of contrasted figures, the 
