Question 20 - Subtest II: Science Practice Test for the CSET Multiple Subjects Test

The similar framework of bones in the hand of a man, wing of a bat, fin of a porpoise, and leg of the horse,— the same number of vertebræ forming the neck of the giraffe and of the elephant,— and innumerable other such facts, at once explain themselves on the theory of descent with slow and slight successive modifications. The similarity of pattern in the wing and in the leg of a bat, though used for such different purpose,— in the jaws and legs of a crab,— in the petals, stamens, and pistils of a flower is, likewise, to a large extent, intelligible on the view of the gradual modification of parts or organs, which were aboriginally alike in an early progenitor in each of these classes.