Contributions to the theory of natural selection. A series of essays ... By Alfred Russel Wallace ...

ILLUSTRATIVE OF NATURAL SELECTION..157
in similar localities, while the males, which frequent
the sunny open river-banks, have a totally different
colouration. In these cases, therefore, natural selection seems to have acted independently of sexual
selection; and all such cases may be considered as
examples of the simplest dimorphism, since the offspring never offer intermediate varieties between the
parent forms.
The phenomena of dimorphism and polymorphism
may be well illustrated by supposing that a blue-eyed,
flaxen-haired Saxon man had two wives, one a blackhaired, red-skinned Indian squaw, the other a woollyheaded, sooty-skinned negress-and that instead of the
children being mulattoes of brown or dusky tints,
mingling the separate characteristics of their parents
in varying degrees, all the boys should be pure Saxon
boys like their father, while the girls should altogether
resemble their mothers. This would be thought a
sufficiently wonderful fact; yet the phenomena here
brought forward as existing in the insect-world are
still more extraordinary; for each mother is capable
not only of producing male offspring like the father,
and female like herself, but also of producing other
females exactly like her fellow-wife, and altogether
differing from herself. If an island could be stocked
with a colony of human beings having similar physiological idiosyncrasies with Papilio Pammon or
Papilio Ormenus, we should see white men living
with yellow, red, and black women, and their offspring always reproducing the same types; so that