On some theoretical and practical aspects of population variability in helminths.

Possibilities of studies of some microevolutionary processes in helminths on the basis of knowledge of their variability are presented. The practical aspects of the study of helminth variability are also referred to. In conclusion the author states that the investigation of non-morphological characters of helminths, in relation to various morphological structures of phenotypes in the populations of parasite and host, represents a sphere in which the interests of theoretical and practical helminthology meet with one another.