290 MONTGOMERY. [VoL. XII. 
C. Direct Inferences from the Tabulated Data. 
(a) It is the rule that, in genera comprising more than one 
species, those species which inhabit small or insular breed- 
ing areas do not evince as much individual variation in the 
dimensions as do species with more extensive and diversified 
breeding areas. This fact becomes at once apparent after a 
study of the Tables I-XII, when a comparison is made 
between species inhabiting small islands, or other restricted 
districts, and those which have a much wider distribution. But 
few exceptions are to be found to this rule. 
(6) It is the rule that species with geographical races, when 
the latter differ from one another in one or more dimensions, 
evince a greater amount of individual variation than do species 
which are not divided into such races, provided that the breeding 
area is approximately equal in extent and diversification in both 
cases. Thus of the nine families tabulated in Table XIV, in 
all, with the single exception of the Falconide@, a greater per- 
centage of geographical races evince variation to the amount 
of 1.5% in two dimensions, than of species which are not split 
into races. If, however, the geographical races of a species 
differ from one another mainly in color (as e.g. those of Cardina- 
lis cardinalis), and less or not at all in dimensions, then as a 
rule they do not evince a greater amount of variation in the 
dimensions than do species without geographical races.1_ In 
Table XIV, further, the percentages in favor of geographical 
races may still be increased, when we consider that many 
species which are as yet regarded as distinct, may in the 
future be classed by ornithologists as subspecies, — resulting 
in a subtraction from the left hand column of percentages, 
and an addition to that on the right. 
(c) It is the rule, subject to the preceding two “laws,” that 
migratory species evince a greater amount of individual varia- 
1 Though I have not investigated in birds the facts of individual co/or varia- 
tion, —a kind of variation of which it is obviously difficult to determine the 
amount, I would be inclined to conclude, @ f77or7, that the races of a species differ- 
ing from one another mainly in color would present a greater amount of color 
variation than would species which are not divisible into color races, other 
factors being equal in both cases. 
