E. Y. Thomson, J. Bell and K. Pearson 
51 
1 scale unit was now found to be 1-46 mm., as against Miss Wright's 1-48 mm. 
The sohition of this difference may lie in (a) a constant relative personal equation 
of the two measurers, (b) a change in Miss Wright's material during the two years 
which have elapsed since the measurements were made. In the case of both 
series the slides were dried for about a month before measurements were made; 
it is possible, however, that an interval of two years would produce a still further 
effect. 
TABLE I. 
Mean Values of Characters in Nest and Population Queens. 
Population Queen 
Nest Queen 
Eatio p. Q.\N. Q. 
Character 
Eight Wing 
Left Wing 
Eight Wing 
Left Wing 
Eight 
Wing 
Left 
Wing 
A 
B 
C 
D 
E 
F 
G 
13-223 + -015 
7-770+ -010 
6-185 + -008 
3-933+ -006 
1-446 + -003 
3-031 + 005 
1-414+ -002 
13-219 + -016 
7-818 + -010 
6-177 + -008 
3-950+ -007 
1-452+ -003 
3-045 + -005 
1-405 ±-003 
13-623 + -008 
8-042 + -006 
6-388 + -004 
3-989 ±-003 
l-457±^002 
3^1 75 + -003 
1-420 ±-002 
13^617 + -009 
8^058+^007 
6^390 +^004 
3-983 + -003 
1-467 + -001 
3-191 ± -003 
1-415 ±^002 
•9706 
•9662 
•9682 
•9860 
•9925 
•9546 
•9958 
•9708 
•9702 
•9667 
•9917 
•9898 
•9542 
•9929 
Mean 
•9763 
•9766 
H 
I 
J 
K 
L 
M 
•2975 + -0004 
-3672 + -0005 
-3605 + -0005 
-5878 + -0003 
-4680+ -0003 
-2293+ 0002 
-2992+ -0005 
•3675+ -0005 
•3565 + ^0004 
•5917 + ^0003 
•4680 + -0003 
•2303 + -0002 
■2928 + -0002 
•3651 + -0004 
•3560 + ^0004 
•5904 + •OOOS 
•4690+^0002 
•2331 + ^0002 
•2925 + ^0002 
•3687 + ^0003 
•3552 + ^0004 
•5918 ± •OOOS 
•4694 + 0002 
•2344 ±^0002 
1-0161 
r0057 
1-0126 
•9956 
•9979 
•9837 
r0229 
•9967 
1 -0037 
•9998 
•9970 
•9825 
Mean 
1-0019 
rooo4 
The difficulty about a personal equation lies in the fact that it would not 
extend in either case to the determination of the magnifying powers, for these 
were found in agreement when determined in the two cases by third observers. 
If the difference be due to the complete dryness of the material after two years' 
storage, this difference is of no importance for our present purposes, as both series 
were measured at practically the same interval after the preparation of the slides. 
Even if we could attribute the divergence to personal equation, i.e. if Miss 
Thomson would have found two years ago, as she does now, that on an average 
she must reduce Miss Wright's measurements by the factor "986, i.e. by about 
l'4p.c., this will not account for the average ratio of "976, i.e. a reduction of 2-4 p.c, 
found between the population of queens and the queens of a single nest. That we 
are dealing with a real differentiation is furthermore indicated by the fact that the 
ratios of the absolute values differ so widely from one character to a second, the 
