After a brief review of the classification and distribution of the orders of the Diplocheta: Julida, “Cambalida” and Spirostreptida, the interrelationship of these groups is discussed mainly on account of the structure of the gnathochilarium and male gonopods. The conclusions are related to the distributional patterns of the groups, and a hypothesis is developed with regard to the possible dispersal of the diplochetan orders and families. It is suggested that the dispersal started in the southern hemisphere and that the northern Diplocheta reached the Holarctic by way of a pacific route, involving the former existence of a “lost” continent Pacifica.