The criteria of the species concept are thus threefold, and each individual point is an applicable test a species requires known traits, it does not beget descendants equally well with individuals of other species, and it does not coalesce into other species. Species are groups of organisms united by a common form, but there is no definite difference that divides them. All constructive theories of evolution have been built upon the understanding that we know if the relation of varieties to species justifies the assumption that the one phenomenon is a phase of the other, and that each species arises. In a work published in 1916 in English, Dutch botanist Johannes Paulus Lotsy proposed both a definition of species and a conception of evolution. Coenospecies are the total sum of possible combinations in a genotype compound and include one or more ecospecies, which include one or more ecotypes, the forms that develop in different ecosystems or habitat types.