PROFESSOR LEIPER, who has been nominated by the Ministry of Agriculture to give this talk, is an authority on the recondite subjects of Helminthology, Parasitology and Protozoology-which, being translated, means that he knows all about the various unpleasant organisms that grow in and feed on living creatures. Amongst many other professional distinctions, he is a member of the Agricultural Research Council, and has accompanied several research expeditions to the tropics under the auspices of the Colonial Office.