I. In the following three experiments it will be shown that ripe eggs of Ascaris suilla can hatch in the intestine of the pig, that the larvae issuing from these eggs enter the body of the pig and pursue the same course through the body as in the rat and mouse. They have been found in the lung of the pig from the 6th to the 8th day and in the trachea on the 8th day. Dead larvae have been found in the faeces of the pig on the 11th day after infection (Expt. 6).