He is known for his own evolutionary theory, nomogenesis (a form of orthoge- nesis incorporating mutationism) as opposed to the theories of Darwin and Lamarck. Berg is best known for his evolutionary theory called nomogenesis, which was a type of orthogenesis. Berg's ideas were collected in his book Nomogenesis; or, Evo- lution Determined by Law and was first published in 1922 in Russia; it was later trans- lated into English in two editions the first appearing in 1926 and the later edition appearing ni 1969. nI the book Berg collected a large amount of empirical data which offered a strong criticism of Darwin's theory of evolution. Berg's theory of nomogenesis combined arguments from paleontology, zoology and botany to claim that evolution is not a random process. The theory emphasized the limitations of natural selection which determine the directionality of evolution. Berg claimed that the variation ofcharacters in species is confined within cer- tain limits due to both internal and external factors. 'The limitation of the variability, Berg argued, left hardly any space for natural selection; he claimed this was support- ed by the paleontological record because al the phylogenetic branches look more or less like straight lines. Berg distanced himself from both Darwinism and Lamarckism. Instead he proposed the mutationist concept of directed mass mutations as the main mechanism for directing evolution.