But this inference
is chiefly grounded on analogy, and it is immaterial whether or not it be
accepted. No doubt it is possible, as Mr. G.H. Lewes has urged, that at
the first commencement of life many different forms were evolved; but if
so, we may conclude that only a very few have left modified descendants.
For, as I have recently remarked in regard to the members of each great
kingdom, such as the Vertebrata, Articulata, etc., we have distinct
evidence in their embryological, homologous, and rudimentary structures,
that within each kingdom all the members are descended from a single
progenitor.
When the views advanced by me in this volume, and by Mr. Wallace or when
analogous views on the origin of species are generally admitted, we can
dimly foresee that there will be a considerable revolution in natural
history. Systematists will be able to pursue their labours as at present;
but they will not be incessantly haunted by the shadowy doubt whether this
or that form be a true species. This, I feel sure and I speak after
experience, will be no slight relief. The endless disputes whether or not
some fifty species of British brambles are good species will cease.
Systematists will have only to decide (not that this will be easy) whether
any form be sufficiently constant and distinct from other forms, to be
capable of definition; and if definable, whether the differences be
sufficiently important to deserve a specific name.
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