140 CLASSIFICATION OF THE FORMS OF ‘THE PRINCIPLES. 
4. Conditions Determining the Forms of Selection. 
The forms of selection depend on the following conditions (the 
letters and numbers are those used in the tables on pages 138-139): 
j. The relations in which individuals of the same group stand to 
each other; that is, the reflexive conditions. First, the aptitudes (1. e., 
instincts and other inherited powers), that shape these relations to 
each other; second, the habitudes (7. e., habits and other acquired 
powers), that shape their relation to each other; and, third, the 
physical characters of the individuals, must be codrdinated. 
k. The relations in which the group stands to the environment, that 
is, the environal conditions (arising from the action and reaction be- 
tween the group and its environment), must be harmonized. 
20. The conditions within the group that shape these relations to 
the environment; that is, the endonomic conditions, being (56) the 
habitudes, and (57) the aptitudes that enable the isolated group to 
determine how it will use the environment, must be kept in the fullest 
possible accord with these uses and with each other. 
21. Heteronomic conditions, (58) natural and (59) artificial; that is, 
conditions in the environment that constitute a limit to the possible 
methods of escape from destruction. Small colonies of Hawaiian 
snails, of the same species, isolated in neighboring valleys, but occu- 
pying the same species of trees and feeding in the same way, and all 
exposed to the same enemies, it seems to me are probably subject to 
the same forms of heteronomic environal selection. Any snail, 
capable of living on several species of trees growing in thick, shady 
groves, when brought to a valley where only one species of such trees 
is found, is subjected to heteronomic conditions, for but one method 
of survival is open to it. But even under these conditions we find 
divergence taking place in isolated groups. Shall we attribute such 
divergence to diversity of selection or to the diversity presented in 
the average character of the groups when first isolated? I believe 
this latter explanation is the more reasonable. If each colony was 
originated bya single snail, we knowit is impossible that these original 
progenitors of the different colonies should in every respect have 
possessed the same characters. It is also impossible that the varia- 
tions occurring in an isolated colony springing from a single pair 
should be exactly the same variations, presented in exactly the same 
proportions, as in the mother colony from which they were separated. 
The influences determining the forms of isolation, partition, and 
election are also presented under the aspects of reflexive influences 
and environal influences, and in constructing terms for the different 
