(a) Where, by the terms of the receipt, the warehouseman undertakes to deliver the goods to the bearer, or (b) where, by the terms of the receipt, the warehouseman undertakes to deliver the grain to the order of a specified person, and such person or a subsequent endorsee of the receipt has endorsed it in blank or to bearer. Where, by the terms of a negotiable receipt, the grain is deliverable to bearer or where a negotiable receipt has been endorsed in blank or to bearer, any holder may endorse the same to himself or to any other specified person, and in such case the receipt shall thereafter be negotiated only by the endorsement of such endorsee.