As Sir J.

Lubbock has remarked, "Every species is a link between other allied forms.

" If we take a genus having a score of species, recent and extinct, and destroy four-fifths of them, no one doubts that the remainder will stand much more distinct from each other.

If the extreme forms in the genus happen to have been thus destroyed, the genus itself will stand more distinct from other allied genera.

What geological research has not revealed, is the former existence of infinitely numerous gradations, as fine as existing varieties, connecting together nearly all existing and extinct species.