a1 From the Department of Parasitology, London School of Hygiene and Tropical Medicine
Six specimens of Xenopus laevis obtained from University College, London, were examined for polystomes; one harboured an adult worm measuring 2·1 mm. in length and two immature specimens, both 0·8 mm. in length, and one was parasitized by a single mature specimen measuring 2·4 mm. in length.