 Philiptschenko distinguished between microevolution and macroevolution because he rejected natural selection in the sense of Darwin as an explanation for larger evolutionary transitions that give rise to taxa above the species level in the Linnean taxonomy.Accordingly, he restricted Darwinian "microevolution" to evolutionary changes within the boundary of given species that may lead to different races or subspecies at the most.By contrast, he referred "macroevolution" to major evolutionary changes that correspond to taxonomic differences above the species level, which in his opinion would require evolutionary processes different from natural selection.