 With respect to his selection experiments mentioned above, Johannsen had furthermore introduced the distinctions between phenotype and genotype. The former concept initially captured the range of fluctuating variation in a quantitative character centering on an average value that characterized a pure line. Later, however, the term was used with respect to an individual’s characteristics for both quantitative and qualitative differences in type. The genotype was the genetically relevant constitution of the germ cells or zygote, in other words, the sum of the genes, where genes could only be identified as bearing differences between genotypes resulting in phenotypic differences. The phenotype was the result of the interaction of the genotype with the environment in ontogenesis (Meunier 2016a; entry on  the genotype/phenotype distinction).  The phenotype of the parents, let alone of more distant ancestors, thus had no effect on the offspring. The genotype was what passed from parents to offspring. Johannsen defined heredity “as the presence of identical genes in ancestors and descendants” (Johannsen 1911: 159).