Abstract
The three species of gregarines described in the present paper—Monocystis cambrensis sp.nov., M. lanceata sp.nov. and M. elongata (Phillips & Mackinnon, 1946), Loubatières, 1949—are all parasites of British earthworms. The observations upon which these descriptions are based form part of a larger survey of the monocystid fauna of several British earthworms. The methods used are fully described in a previous paper (Rees, 196).