A method of recovering cysts from soils of not more than 10% water content is described. The method is continuous and the yield from it is only slightly lower than that from the dry flotation of soil. The yield was found to contain a slightly lower percentage of full cysts than that obtained by dry flotation but this drop was not considered sufficiently great to justify the drying of soil in large quantities. Quantities of soil in the neighbourhood of 1 cwt. can be handled continuously in a matter of two hours.

The migrations of infective larvae of sheep and horse Strongyles have been studied by various workers, principally in relation to their behaviour in faeces or in different types of soil. (Bruns, 1937 and Lucker, 1938). The factors affecting the extent and nature of the migrations of certain infective larvae on to grass have also received attention (Rogers, 1940). A knowledge of the behaviour of larvae both in soil and on grass is very necessary if control methods either by chemicals or by controlled pasturing are to be effective. The present paper, however, describes an attempt to study the fundamental behaviour of these larvae in the laboratory, in the hope of obtaining results of practical value or of filling up certain gaps in our knowledge of them. A simple technique was sought, whereby the migrations of the larvae could be studied in the laboratory under different conditions, and is described herein.

At known periods the infectivity, fat content and activity of larvae of Haemonchus contortus aged at 7°C, 24°C. and 37°C, were examined.

The relationship between fat content, activity and infectivity was found to be fairly close in rapidly aged larvae. In slowly aged larvae the infectivity fell more rapidly than the other factors.

The genus Heterodera comprises three species, the root-knot nematode, H. marioni (Cornu 1879) Goodey 1932, and the two species in which cysts are produced. These are, H. schachtii Schmidt 1871, which is associated with disease in potatoes, sugar beet, cereals, peas and some other crops, and H. punctata Thorne 1928, which has caused disease of wheat in Canada, and has been found in this country infesting a common grass Agrostis stolonifera L.