Note 2 — Chapter I · THE PRESENT CRISIS IN EVOLUTIONARY THOUGHT

The term mutation had been used long before and in a similar sense by the German palæontologist Waagen, who employed it to designate the variations of a specific type that succeed one another in successive strata, a thing which rarely occurs. (Cf. Waagen’s Die Formenreihe des Ammonites subradiatus, Geognost. paläont. Beitr., Berlin, 1869.)