A Second Meeting to discuss this paper has been arranged and will be held at 11, Upper Belgrave Street, London, S.W. 1 , on Wednesday, 24th May, 1944, at 5.15 P.M. Written contributions) to the discussion are invited, and it is requested that thse be sent to the Secretary at least a week before the date of the meeting, so that the Author in his reply may include any points raised by correspondents.