He read Lyell's second volume and accepted its view of "centres of creation" of species, but his discoveries and theorising challenged Lyell's ideas of smooth continuity and of extinction of species.
Han læste Lyells andet bind og accepterede dets syn på "centrer for skabelse" af arter, men hans opdagelser og teoretiseringer udfordrede Lyells ideer om jævn kontinuitet og om arters uddøen.