Under laboratory conditions the preparasitic stages of Stephanurus den-tatus were completed in 5-6 days. Low temp. retarded development of eggs and larvae. The vitality of the infective larvae was destroyed at[long dash]19[degree] C. in 9 hrs., and also when they were air dried on a slide for about 30 min. The infective larvae were incapable of penetrating the intact skin of pigs. Migration in the body is from the intestine to the liver by way of the portal vein. From the liver the larvae may wander to the lungs; they can also reach the lungs by way of the lymphatics. By perforating the capsule of the liver the agamic worms reach the abdominal cavity, from which they may enter into the perirenal fat. They also bore into other tissues with which they come in contact.