Aphelenchoides arcticus n. sp. and A. parasaprophilus n. sp., collected from soil around roots of moss, are described and figured. Both species are closely related to, and are compared with, A. parietinus (Bastian, 1865) Steiner, 1932; A. helophilus (de Man, 1880) T. Goodey, 1933; A. blastophthorus Franklin, 1952; A. saprophilus Franklin, 1957; A. composticola Franklin, 1957; A. sacchari Hooper, 1958; and A. subparietinus Sanwal, 1961.

A key for the identification of 35 species of the nematode genus Aphelenchoides Fischer, 1894 is given. The key is based on the characters of the females. The chief characters used in the key are as follows: shape of female tail, structure of stylet, presence or absence of postvulvar uterine sac, position of excretory pore and nerve ring, and number of lateral incisures. The descriptive terms used in the key are illustrated by line drawings. A separate key is provided for species where only males are known.

Chambersiella bakeri n. sp., collected from the bark of an oak tree in the vicinity of Richmond, Ontario, is described and figured. It differs from C. rodens in the structure of the stoma, in the form of the female reproductive system, in the position of the vulva, and in the size of the body. With the new information provided by this species the generic diagnosis of Chambersiella Cobb, 1920 is emended. This genus, after emendment, is removed from the family Cephalobidae Chitwood and Chitwood, 1934 and placed in Chambersiellidae n. fam. The relationships of Chambersiellidae with the Rhabditidae and the Cephalobidae are discussed.

Chambersiella bakeri is transferred to a new genus, Geraldius. Diagnoses of the genus Chambersiella and family Chambersiellidae are emended. Subfamily Chambersiellinae is reinstated to include the genera Chambersiella, Geraldius, Diastolaimus, and Santafea, and a new subfamily Macrolaiminae is established for the species of Macrolaimus. A key to the subfamilies and genera of Chambersiellidae, based on the presence or absence of cephalic cirri, shape and structure of stomatorhabdions, and the number of female gonads, is given.

A direct infestation method as a means of rearing pure populations of A phelenchoides ritzemabosi is described. A mature female is placed directly on the ventral surface of the leaf on a tiny droplet or a thin film of water. Reproduction takes place after successful entry of the nematode into the leaf tissue. The progeny of this female is then transferred to new leaves and the procedure is continued. Methods of maintaining high humidity around the leaves are described. The use of 'mist propagation frames' to enhance the spread of disease in greenhouse beds is recommended.