Many parasitic nematodes possess free-living stages in their life cycles which feed and grow in an open environment in the same way as free-living organisms. The parasitic stage of the cycle is spent within the host. In Bunostomum trigonocephalum, which is a hookworm of sheep and goats, the parasitic stage inhabits the small intestine of the host, while Graphidium strigosum parasitises the inner wall of the stomach of the rabbit and hare. Both of these parasites are blood-suckers and reasons for their discrimination with regards to their foci are not fully established.

In a collection of parasites sent to the Institute of Parasitology from Egypt by Dr. R. E. Kuntz and Mr. S. M. Malakatis from various genera of rodents were nematode parasites from 23 specimens of Arvicanthis niloticus (African striped mouse, spine rat, Kusu). Numerous subspecies of Arvicanthis niloticus have been reported from Arabia, Uganda, Abyssinia, Somaliland, Kenya, Tanganyika, East Congo, Asben, Gold Coast, Sierra Leone, Portuguese Guinea, South to North Rhodesia and Egypt. [...]

Placoconus lotoris (Schwartz, 1925) Webster, 1956 is an intestinal nematode parasite of North American raccoons and skunks. It is a hookworm belonging to the family Ancylostomatidae Looss, 1905, sub-family Bunostomatinae Looss, 1911. The parasite was originally described by Schwartz (1925) who named it Uncinaria lotoris. Chandler (1942) transferred it to the genus Arthrocephalus Ortlepp, 1925. Webster (1956) placed the worm in a new genus, Placoconus. Although Placoconus lotoris has been known for a comparatively long time, very little work has been done on its biology. The parasite when present in large numbers appears to affect adversely the health of the raccoon which is one of the fur-bearing animals of North America.

The nematode parasites studied were collected from a large number of wild rats, Rattus rattus, on the island of Formosa by the United States Navy Medical Unit No.2 under the direction of Commander R. E. Kuntz. Rattus rattus belongs to the group of mammals, Rodentia, the members of which are characterized by their gnawing and chewing habits. They are vegetarians and have a world wide distribution. Representatives of all the large groups of parasitic nematodes have been recorded from rodents; the parasitic nematodes of the common rat, for example, have a cosmopolitan distribution.

The following work is based on the study of some nematodes collected in Formosa from two hosts, Suncus murinus and Bandicota nemorivaga. It deals with the taxonomy of the nematodes, with their hosts and with their geographical distribution range.

The following work is based on a study of the trematodes collected from the fishes of Lake Hertel. It deals with the taxonomy of the trematodes and with some of the relationships between the host and the parasite. Lake Hertel is situated at an elevation of 570 feet on Mont St. Hilaire one of the Monteregion Hills in the St. Lawrence Lowlands. The lake measures about 2,000 feet in length and in width. It has a surface area of between 75 and 80 acres and a maximum depth of between 24 and 30 feet depending on the season of the year. The shoreline is regular and most of the bottom is of a fine dark mud. There is little variety in the type of habitats available to the various species of fish and their parasites.

Collections of snails were made during spring, summer and fall of 1963 along the Ottawa River in the vicinity of Ste. Anne de Bellevue, near Montreal, Quebec. This area is inhabited by muskrats and frequented by many migratory birds. The river contains an abundance of fish and frogs, making it an ideal place for this study. One species of snail, Lymnaea catascopium pallida (Adams) is abundant in this area and harbours many species of larval trematodes. An intensive investigation of this species of snail revealed that only cercariae belonging to the following genera: Cotylurus flabelliformis (Faust, 1917) Van Haitsma, 1931, Diplostomum flexicaudum (Cort and Brooks, 1928) Van Haitsma, 1931, Echinostoma revolutum (Froelich, 1802) Looss, 1899, Plagiorchis muris Tanabe, 1922 and P. proximus Baker, 1915, were present in any numbers.

The literature on the biology of Trichinella spiralis is full of many confusing and conflicting reports. The reviews of Reinhard (1958) and Schwartz (1960) of the early work on T. spiralis show that the unique character of the biology of this worm confounded the early workers, who attempted to unravel its entire life cycle. [...]

Many writers, including Cameron (1938), and Linton (1897) have shown the necessity of studying the parasites of freshwater fishes. Cameron (1938) pointed out, that Canada, with its one-eighth million square miles of freshwater, has an extremely valuable population of commercial and game fish which harbour parasites of both medical and veterinary importance. [...]

The genus Entamoeba Casagrandi et Barbagollo, 1895, from the standpoint of pathogenicity and number of different hosts affected is the most important of all the genera of parasitic amoebae. [...]