On the topical problems of species in general and in relation to helminths

In the light of the present knowledge of species, the author suggests to accept ten features of species and the general definition of species proposed by Zavadsky (1961, 1968), together with the definition by Mayr (1940) characterizing more concretely the species at the level of biparentally reproducing organisms. The definition by Timofeeff-Ressovsky et al. (1973) may be used for exclusively autogamous species of helminths. From the viewpoint of the species as a taxonomic unit, the paper presents proposals for establishment of a practical standard which would better suit the theoretical idea about the helminth species than it was the case till the present.