Note 661 — Chapter XVII · ON THE THEORY OF TRANSFORMATIONS, OR THE COMPARISON OF RELATED FORMS*

Cf. W. B. Scott (Amer. Journ. of Science, XLVIII, pp. 335–374, 1894), “We find that any mammalian series at all complete, such as that of the horses, is remarkably continuous, and that the progress of discovery is steadily filling up what few gaps remain. So closely do successive stages follow upon one another that it is sometimes extremely difficult to arrange them all in order, and to distinguish clearly those members which belong in the main line of descent, and those which represent incipient branches. Some phylogenies actually suffer from an embarrassment of riches.”