Variability in testis position and number of a strain of H. diminuta from laboratory rats is compared with variability of the same strain of H. diminuta experimentally introduced into the ground squirrel C. leucurus. Similar results were obtained for both exptls. and controls. The characteristics of both groups of specimens were similar to those of H. diminuta from other localities and hosts. H. diminuta in C. leucurus did not adopt any of the characters of H. citelli from ground squirrels.