m VARIABILITY OF SPECIES IN A STATE OF NATURE 63 
virginianus are registered, we see a remarkable spreading out 
of the spots, showing in some of the characters a tendency to 
segregation into two or more groups of individuals, each vary¬ 
ing considerably from the mean. 
In order fully to appreciate the teaching of these diagrams, 
VARIATION OF 
ICTERUS BALTIMORE. 20.<? 
• • 
• • 
7i)i7. 
JL 
• • • • 
Wi. 
V 9 - 
Tarsus. 
• • 
Middle Toe. 
• • • • • 
•••••••• 
Hind Toe. 
/• 
• •• • 
Bill, 
:::: 
Length. 
Bill, 
m • • • 
e • 9 • c 
Width. 
• • 
Fig. 9. 
we must remember, that, whatever kind and amount of varia¬ 
tions are exhibited by the few specimens here compared, 
would be greatly extended and brought into symmetrical 
form if large numbers—thousands or millions — were sub¬ 
jected to the same process of measurement and registration. 
We know, from the general law which governs variations 
from a mean value, that with increasing numbers the range 
