Three species, and one variety, of the pseudophyllid genus Bothridium de Blainville, are known to occur in pythons. B. ovatum occurs in the African python (P. sebce): B. pythonis in the Indian python (P. molurus) and B. pythonis var minor in P. reticulatus, the Indo-Malayan python; while Maplestone and Southwell (1923, p. 317) record another species, B. ornatum from the Australasian python (P. spilotes var variegatus). The literature on this genus appears, so far, to have dealt only with morphology and taxonomies. Joyeux and Baer (1927, p. 126) describe the anatomy and relationships of B. ovatum, B. pythonis and B. pythonis var. minor. Braun (1894–1900, p. 1690) gives a brief description, accompanied by very detailed figures, of the anatomy of B. pythonis and also figures the embryonated ovum (pi. Iviii, fig. 8). This is the only figure of any developmental stage of the parasite which the writer has been able to discover. Southwell (1930, p. 58) records the worm from P. reticularis and P. molurus, in Bengal, Nepal and Ceylon, and summarises its anatomy. He also mentions its occurrence in a tiger which he thinks had been eating a python. No account of the life-cycle of any species of Bothridium appears to have been written. When, therefore, in February, 1932, some living Bothridium arrived in the Helminthology Department, it was resolved to discover how far its development resembled that of other better-known Psuedophyllids.