This fungus was found in rotting vegetable matter from the floor of Ashtead Wood, near Leatherhead, Surrey, England. Small portions of the material sown on plates of sterile maize-meal agar gave rise to a mixed culture of moulds, amoebae and other microscopic animals in which nematode worms were plentiful, and about a month after inocu? lation nematodes of various species were being preyed upon by a fungus with a mycelium of sparingly branched, non-septate hyphae about 5 /x wide. The eelworms were attached to the hyphae by means of a sticky secretion which could be clearly seen under the microscope as the ani? mals struggled in vain to free themselves; this adhesive material was colourless, and appeared to be of about the viscosity of treacle. It was secreted copiously by the mycelium at the point where the eelworm was held, and it appeared to be produced only on contact with the prey, as no trace of it could be seen on other parts of the mycelium. After a period of violent struggling the captured eelworm finally became quiescent and, apparently, moribund. An outgrowth from the fungus at the point of contact then penetrated the integument of the nematode and from this penetration branch a system of non-septate trophic hyphae grew out, eventually filling the carcass of the eelworm and absorbing its contents (Fig. la, b). The trophic hyphae were a little smaller in diameter than the filaments of the main mycelium. Conidia were produced abundantly after an initial period of feeding. The fertile hyphae were long, rising slender and erect to a height of 300-500 ll, and each bore at its apex a large conidium. Sometimes a second spore was formed after further elongation of the conidiophore (Fig. \c). The conidia were obovoid or pyriform, (22-)27-61 fx long and 13-26/x across their greatest diameter (Fig. ld). In spite of their great size they were produced in abundance. No sexual reproduction took place, although the cultures were kept under observation for several months. Attempts to isolate the fungus by picking off conidia and placing them aseptically on sterile maize-meal agar and sterile rabbit dung agar failed, as the spores did not germinate. This is in accordance with experience, for I have on former occasions