The vast majority of the helminthic parasites of man are represented among those animals which are in close contact with man, either by the same species or at least, by closely related forms. A very noticeable exception is Enterobius vermicularis. Possibly owing to its special life-history, it has become highly specialised for its human host and to find its closest relations, it is necessary to examine the forms found in primates.The object of this paper is accordingly to systematise our knowledge of the oxyurid worms found in this group.As Enterobius vermicularis is the most important of these, it has been found desirable to briefly re-describe its anatomy, followed by that of the related species, in apes, in monkeys and other primates.

Experimental infections in rodents with Echinococcus multilocularis sibiricensis, Echinococcus granulosus canadensis, and Echinococcus granulosus (Lebanon origin) both by ingestion of onchospheres and by parenteral injection are recorded. The microscopic anatomy of the larval parasite and of the host reaction are discussed and illustrated in detail. Voles and cotton rats display little resistance to the development of the cyst of E. m. sibiricensis and ultimately destroy the host, while collared lemmings and golden hamsters overcome the cyst and destroy it. Muskrats and certain white mice are intermediate in their effects. In all cases, however, some degree of degeneration of the parasite into the alveolar form is shown. White rats, guinea pigs, and rabbits could not be infected with this parasite. E. g. canadensis was developing in the lung of one AKR strain mouse while in the chinchilla the parasite commenced to develop in the lung but was overcome at an early stage. No development took place in the other species of hosts. E. granulosus (Lebanon) appeared to be developing successfully in some cotton rats and white mice fed on onchospheres.

A possible new variety of cestode, Raillietina (R.) demerariensis var. trinitatae, and two new varieties, Trichuris gracilis var. trinitatae and Aspidodera binansata var. agoutiae and a new species of nematode, Helminthoxys urichi are recorded from the agouti and lappe from Trinidad, B.W.I.

During the examination of an abnormal specimen of the Scottish Red Deer (Cervus elaphus) in the winter of 1930, my colleague, Mr. W. C. Miller, M.R.C.V.S., discovered several specimens of a bursate nematode lying on the connective tissue between the latissimus dorsi and the external intercostal muscles. Struck by the unusual habitat of such a worm, search was subsequently made in similar situations in other deer, and in two animals the same parasite was found.

Tænia echinococcus has always been recognised as one of the most important tapeworms of carnivores, both from the human and the economic point of view. Its intermediate stage, or Hydatid, assumes many forms, but most modern workers believe that all these forms—with one possible exception, the alveolar form from Central Europe—are merely the manifestations of a single species.

Six species of Trichostrongylidæ are described in this paper. Four are previously recorded species which were insufficiently known and described.

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1. From an examination of over 700 sheep of Scottish origin a list of the parasites found in the intestinal tract has been prepared.2. The commonest parasite found is Monodontus trigonocephalus, a worm which occurs also in goats and cattle. This parasite can be found at any season.3. Nematodirus sp. also is extremely common during the warmer months.4. From a systematic geographical examination of sheep it has been ascertained that Monodontus trigonocephalus occurs in every district in Scotland ; and of 40 sheep examined in this part of the enquiry, 38 were found to be infected. Thirty specimens have been recovered from an apparently healthy sheep, but usually the number is much smaller (7–10).