Intraspecific Variation in Parasitic Flatworms

Abstract

AT THE outset of our discussion it 11 would be useful, I believe, to stake out the areas and list the items on which there is general agreement. It is admitted that exist, and that the is the basic unit in taxonomy. Further, it is agreed that taxonomy has two primary functions or obligations, one of which is to designate each in a distinctive and permanent manner, so that it is and will continue to be identified by the same cognitive symbol or name. The second task i-s the formulation of a system of classification which will express evolutionary sequence and genetic relationship of fossil and living organisms. It has been stated that John Ray (1686) first introduced into natural history an exact concept of species, and it pertainedto plants rather than animals. At that time and for the next century, the idea of fixity of species was accepted; that idea precluded the taxonomic problems which confront us today, and Linnaeus in the Systema Naturae was able to name and classify many common animals, which remain as accepted, valid species.