The earliest success of Bass1in the cultivation of certain parasitic protozoa (plasmodia)in vitroled one of us (Wellman) to attempt the nurture in artificial mediums of the embryos ofFilaria immitisLeidy. At that time a considerable number of positive cultures was obtained, using defibrinated dog's blood inactivated for long periods of time at comparatively low temperatures. Since the return of the malarial expedition of the Tulane University Department of Tropical Medicine from Central America additional work has been completed, employing their technic2and comparing results with ordinary blood-cultures. A fuller statement of the work thus far accomplished and the details of future progress will be presented later. Experiments were devised to determine the influence of various whole bloods, serums and diverse mediums, and also the effects of temperature, air, etc., on the cultures. The embryos live for ten or twelve days in some specimens of