Note 375 — Chapter XIV

It was hinted at by Tiedemann. "It is clear that, proceeding from the earlier to the more recent strata, a gradation in fossil forms can be established from the simplest organised animals, the polyps, up to the most complex, the mammals, and that accordingly the animal kingdom as a whole has its developmental periods just like the single individual organism. The species and genera which have become extinct during the evolutionary process may be compared with the organs which disappear during the development of the individual animal" (p. 73, 1808).