AN EXPERIMENTAL APPROACH TO THE ROLE OF RATTUS-RATTUS AND RATTUS-NORVEGICUS IN THE GUADELUPEAN SCHISTOSOMA-MANSONI FOCUS - THE COMPARATIVE-STUDY OF THE DEVELOPMENT OF S-MANSONI IN 2 NATURAL HOSTS (RATTUS-RATTUS AND RATTUS-NORVEGICUS) AND IN 2 LABORATORY HOSTS (THE WHITE-MOUSE AND THE WHITE-RAT)