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.

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