During my undergarad days I was told that Ascaris eggs survived pickling in formalin. Never put it to the critical test though. DAJ David A. Johnston Research Fellow, Dept of Zoology, The Natural History Museum, Cromwell Road, South Kensington, London SW7 5BD. England (tel 071 9389297, fax 071 9388754, email daj at nhm.ac.uk)