Though his suspicions about the Falkland Island fox may have been unsupported, the differences in Galápagos tortoises between islands were remembered, and he later wrote that he had been greatly struck from around March 1836 by the character of South American fossils and of species on the Galapagos Archipelago, noting "These facts origin (especially latter) of all my views".
Aínda que as súas sospeitas sobre o raposo das illas Falkland puideron non ter fundamento, as diferenzas na tartaruga das Galápagos entre illas foron lembradas, e posteriormente escribiu que quedou grandemente impresionado desde marzo de 1836 polo carácter dos fósiles de Suramérica e das especies do arquipélago das Galápagos, anotando que "Estes feitos orixinan (especialmente máis tarde) todos os meus puntos de vista".