Evolution by common descent was soon accepted as historical reality. The theory of natural selection remained heavily debated for about 60 years after Darwin proposed it. Numerous theories were proposed in its stead:
Neo-Lamarckism: inheritance of modifications acquired during lifetime. Such modifications might have been due to the direct effect of the environment on the development (plants with thicker leaves when in a hot, dry environment)
Orthogenesis: straight-line evolution, variation is directed toward fixed goals.
Mutationist theories: natural selection is not necessary to account for the origin of species ->new phenotypes arise by mutation and these mutant forms constitute new species. (Hugo de Vries).