species has a narrow range and
is rare? Yet these relations are of the highest importance, for they
determine the present welfare, and, as I believe, the future success and
modification of every inhabitant of this world. Still less do we know of
the mutual relations of the innumerable inhabitants of the world during the
many past geological epochs in its history. Although much remains obscure,
and will long remain obscure, I can entertain no doubt, after the most
deliberate study and dispassionate judgment of which I am capable, that the
view which most naturalists entertain, and which I formerly
entertained--namely, that each species has been independently created--is
erroneous. I am fully convinced that species are not immutable; but that
those belonging to what are called the same genera are lineal descendants
of some other and generally extinct species, in the same manner as the
acknowledged varieties of any one species are the descendants of that
species. Furthermore, I am convinced that Natural Selection has been the
main but not exclusive means of modification.

* * * * *

{7}

CHAPTER I.

VARIATION UNDER DOMESTICATION.

Causes of Variability--Effects of Habit--Correlation of
Growth--Inheritance--Character of Domestic Varieties--Difficulty of
distinguishing between Varieties and Species--Origin of Domestic
Varieties from one or more Species--Domestic Pigeons, their Differences
and Origin--Principle of Selection anciently followed, its
Effects--Methodical and Unconscious Selection--Unknown Origin of our
Domestic Productions--Circumstances favourable to Man's power of
Selection.

When we look to the individuals of the same variety or sub-variety of our
older cultivated plants and animals, one of the first points which strikes
us, is, that they generally differ more from each other than do the
individuals of any one species or variety in a state of nature. When we
reflect on the vast diversity of the plants and animals which have been
cultivated, and which have varied during all ages under the most different
climates and treatment, I think we are driven to conclude that this great
variability is simply due to our domestic productions having been raised
under conditions of life not so uniform as, and somewhat different from,
those to which the parent-species have been exposed under nature. There is
also, I think, some probability in the view pro