Extract Programmes of control of hydatid disease periodically raise the question: How long do hydatid cysts and eggs remain alive after removal from their hosts? The following tests supplement records made by other workers (e.g., Clunies Ross, 1929 Ross, I. Clunies . 1929. Observations on the Hydatid Parasite (Echinococcus granulosus) and the control of Hydatid Disease in Australia, C.S.I.R.O. Bulletin No. 40 1–63. Melbourne, , Australia [Google Scholar] ).