Abstract 1. 1. Experiments have been accomplished in which microfilariae ( Dirofilaria immitis) have been perfused through the normal popliteal lymph nodes of dogs. It has been shown that there is no phagocytic filtration of the organisms and that they pass through the nodes with comparatively slight hindrance, differing from bacteria and even from the dog's own red cells which are phagocytosed in the nodes, leaving the perfusate practically free of them when collected from the efferent vessel. 2. 2. It has been shown that microfilariae of Loa loa although sheathed are more motile, i.e., they travel farther per minute, than do those of Dirofilaria which possess no sheath. 3. 3. By analogy it is suggested that microfilariae of Wuchereria bancrofti deposited in the lymph stream will not be measurably impeded by lymph nodes in their journey to the blood stream, and that if mechanically checked in nodes normal organisms will not suffer by such residence.