1. The protozoa reported from animal-parasitic helminths are summarised in three tables, with a few comments on some of the more interesting forms.
2. The microsporidian found hyperparasitic in Moniezia expansa and M. benedeni of sheep in England, and Moniezia sp. from a buffalo calf in Pakistan has been found to be identical with Nosema helminthorum described by Moniez, 1887, Plistophora helminthophthora Labbé, 1899, and Nosema bischoffi, Weiser, 1951. The valid name for the organism is therefore Nosema helminthorum Moniez, 1887.
3. The macroscopic and microscopic changes in parasitized tapeworms have been described, and it is believed that the microsporidian is not pathogenic.
4. The host distribution and the geographical distribution of Nosetna helminthorum have been dealt with. This parasite has so far been reported from France, Germany, Yugoslavia, Great Britain and Pakistan, and it is likely that, it will eventually be reported from other countries in which Moniezia is present.