Five new species of Tylenchus Bastian, 1865 from the Canadian high Arctic are described. T. neodavainei n. sp., differs from T. davainei in having finer annules on the lip region and a more slender body. T. stylolineatus n. sp. differs from T. (Tylenchus) arcuatus in having a lower lip region, finer lip annulation, and spear knobs rounded. T. hazenensis n. sp. differs from T. (Filenchus) thornei in not having an offset lip region which is finely annulated and a needle-shaped tail terminus. T. hazenensis differs from T. (Filenchus) ruatus in the ratio between the anterior and posterior portions of the spear length, the tail proportionally shorter and broader, and the basal esophageal bulb not exceptionally elongated. T. aquilonius n. sp. differs from T. (Filenchus) orbus in having a more slender spear, an ovate median bulb, excretory pore well posterior to the nerve ring, and coarser body annulation. T. cylindricaudus n. sp. differs from T. aquilonius n. sp. in having a slender body, the tail more cylindrical, and body annulation indistinct.

A cause of swimmer's itch in the lower Ottawa River is Trichobilharzia cameroni sp. nov. Its life cycle has been completed experimentally in laboratory-bred snails and in canaries and ducks, and the various stages are described. The eggs are spindle-shaped. The sporocysts are colorless and tubular. Mother sporocysts become mature in about a week. The younger daughter sporocyst is provided with spines on the anterior end and becomes mature in about three weeks. The development in the snail requires from 28 to 35 days. A few cercariae were found to live for up to 14 days at 50 °C., although their life at 16° to 18 °C. was about four days. Cercariae kept at room temperature for 60 to 72 hr. were found infective. The adults become mature in canaries and pass eggs in about 12 to 14 days. Physa gyrina is the species of snail naturally infected. It was found in one case giving off cercariae for five months after being kept in the laboratory. Domestic ducks were found to become infected until they were at least four months old, with the parasites developing to maturity in due course; no experiments were made with older ducks. Furthermore, miracidia were still recovered from the faeces four months after the duck had been experimentally infected, and it is suggested that migratory birds are the source of the local infection.

Nematodes having the general characters of Ditylenchus destructor Thorne, 1945, from the potato, bulbous iris, and dahlia, did not reveal any significant difference in the basic structures to suggest the presence of more than one species. However, due to host influence, there may be some variation in total length, width, number and arrangement of sex cells, length of oesophagus, length of spear, and tail shape. Nematodes from potato were successfully transferred to dahlia and carrot, and from iris and dahlia to potato.Specimens of D. destructor from potato interbreed freely with specimens from bulbous iris and from dahlia. Evidently these nematodes from the three hosts are the same species, i.e., D. destructor.Among the ratios used, the values of c in the case of males and that of "V%" have some support from the data.

Specimens of a pure line population of D i t y l e~~c l~z~s destrz~ctor were stuclied. The female reproductive system is well differentiated into the ovary, oviduct, and uterus. The last is further dilfercntiated into the seminal receptacle, cluadricolun~ella, and uterus proper. There is a post~~terine pouch, and this, with the vulva, is also described. The functional regions of the male reproductive systenl arc distinct: the testis, vas deferens, seminal vesicle, and ejaculatory duct.71'l~c posterior ends of the two subventral esophageal glands extend cauclad to about the sallle level, each nrith a small n~~c l e u s .The large dorsal gland, with a conspicuous, larger nuclei~s, extends behind the esophago-ir~testind junction. l'he esophageal tube leaves the e s o p h a g~~s on the inner surface of the dors;ll gland, just behind the subve~ltral glancls, where it joins the intestine. A pair of very small cells guard the entrance of the esophagus into the intestine. lh11an~~srript rcccivetl >Iay 1, 1958. Contribution KO. 3789,

Paratylenchus projectus collected from various areas in Canada and 10 populations, each propagated from a single larva, were studied. Spear length varied from 24 to 28 μ, rarely 29 μ. Sides of head region were straight with a truncate front. Tail terminus varied from conically rounded, rounded, digitate, to subacute. Its differences from Paratylenchus neoprojectus are discussed. A study of the topotypes and lectotype of P. nanus indicates that these are different species. The lectotype is judged to be consistent with the original description, while the topotypes are closely related to P. projectus. A key to the Canadian species of Paratylenchus is presented.