No abstract

1. Four stages in the development of Choanotaenia crassiscolex are described with the help of five text figures and one plate.2. The functional anatomy of the cysticercoid is given with the help of diagrams.3. The identification is based on comparisons with material at the British Museum of Natural History, South Kensington, London, and comparison is made with earlier records in Table 1.4. The unusual cyclophyllidean scolex is discussed and tentative suggestions and queries concerning the general form of the early cysticercoid are put forward.5. An attempt is made to determine more precisely than has hitherto been done for cysticercoids, the relationship of parasite and host.

1. Eubothrium crassum (Bloch) is re-described with additional information about the scolex and genitalia.2. Specific differences between E. crassum and E. salvelini are commented upon and figured.3. The second portion of the uterine duct lying between the central chamber of Mehlis's gland and the uterine sac is established as the “fertilization chamber”.4. Polar bodies and maturation divisions are described and figured in definite relationships with the ovum as evidence of normal maturation in a cestode.5. The position of the receptaculum seminis is determined and a new name, the “vagina sac”, is given to what was previously described as a receptaculum seminis. It is thought to serve for propulsion of male and female cells into the uterine duct.