The article raises and discusses the old question of inheritance of the so-called acquired characteristics, which has not yet become obsolete in the theory of scientific evolution. Its vitality is evidenced by the revival of neolamarckism, which derives its ideas from a new branch of genetics – epigenetics. In the 20th century, the principle bloomed during the period of the dictatorship of Lysenko’s agrobiology. The authors observe the similari­ties between the so-called epigenetic changes and those that used to be called long-term modifications. The molecular biological mechanism of their origin and inheritance has been discovered and is now studied. The author provides a conceptual assessment of these changes, according to inherited characteristics must be distinguished as those that are in­herited unconditionally and conditionally. The former are the mutations that directly affect the genetic structure of the DNA, the latter are the epimutations that affect it indirectly.