A modification of Cobb's decanting and sieving technique is described which was found to combine speed of operation with efticiency when extracting Xiphinema and Longidorus species from a variety of soils. Standard times were set for sedimentation and the nematodes were collected on a bank of sieves each of 150 , u aperture (rather than of a range of apertures) before final separation from inert debris on a Baermann funnel.Preliminary tests showed that both time and temperature could have considerable effect on yield during the final separation stage. X . diversicaudaturn and X . vuittenexi showed different temperature optima at which * This work formed part of a thesis approved for the award of a Ph. D. in the University of London. t Now at Plant Pathology Laboratory, Hatching Green, Harpenden, Herts.

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Systematic sampling of field populations of Xiphinema diversicaudatum, a Xiphinema sp., X. vuittenezi, Longidorus macrosoma and L. profundorum showed that eggs were produced only during a brief period in early summer, but the proportions of each larval and adult stage in the populations showed no comparable annual cycle. Culture studies of X. diversicaudatum and X. vuittenezi, begun with single stages in isolation, showed that several months may elapse between moults, and confirmed that development from egg to adult takes at least two years. It is highly probable that the other three species conform to this pattern. The life span of these species seems commonly to be between 3 and 5 years, and in some individuals may considerably exceed this period.

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