From the second edition (1989):

combining form of Gr. νῆµα, νήµατος thread, used in a number of scientific terms, as ˈnematoblast, Biol. a blastema which develops into a spermatozoon. ˌnematoˈcalycine a., pertaining to, of the nature of, a nematocalyx. ˈnematoˈcalyx, Zool. a calyx containing nematocysts, occurring in some Hydromedusæ. ˌnematoˈceratous a., Entom. having filiform antennæ (Mayne 1856); so nemaˈtocerous a. ˈnematocide, a substance or preparation employed to kill nematode worms. nematoˈcidal a., characteristic of a nematocide. ˈnematogen, Biol. [ad. Fr. nématogène (E. van Beneden 1876, in Bull. Acad. R. Belgique 2 Sér. XLI. 1195)], in Dicyemids, the form which produces a filiform embryo; hence ˌnematoˈgenic, nemaˈtogenous adjs. ˈnematognath, Zool. a fish of the sub-order Nematognathi; a catfish; also ˌnematoˈgnathous a. ˌnematoˈneurous, -ˈneurose a., Zool. of or pertaining to the Nematoneura, Owen's name for a division of Radiata ‘in which nervous filaments are always distinctly traceable’. †ˈnematopode, Zool. a cirriped; also nemaˈtopodous a. (Mayne 1856). ˌnematoˈthec(i)ous a., Bot. of or belonging to a filamentous family of gymnocarpous mushrooms (Mayne 1856). ˌnematoˈzooid, Zool. one of the stinging filaments of a siphonophore considered as a zooid.

1886 Encycl. Brit. (ed. 9) XX. 413/1 A central cavity‥from which the tails of the incipient spermatozoa or ‘*nematoblasts’ project into the lumen of the duct. 1943 Phytopathology XXXIII. 1174 The *nematocidal effect of chloropicrin was tested in the field against the root-knot nematode, Heterodera marioni. 1973 Biol. Abstr. LVI. 6884/2 Nematocidal activity, similar to that of trichothecin, was detected in mycelial extracts and volatile substances of Arthrobotrys, a predacious fungus. 1898 Daily News 4 Aug. 2/1 That the‥antiseptic remedy thymol will be of service as a *nematocide. 1888 Rolleston & Jackson Anim. Life 815 The first-named [a monogenic Dicyemid] produces only vermiform embryoes, and is hence a primary *Nematogen. 1896 Cambridge Nat. Hist. II. 94 Other individuals which produce a more elongated larva‥are called Nematogens. 1899 Zoologischer Anzeiger XXII. 171 The mother of vermiform embryos is called a *nematogen, the mother of infusoriform embryos a rhombogen. 1972 Sci. Amer. Dec. 98/2 Two different wormlike stages of the Mesozoa have been described: ‘nematogens’ were reported to produce nematogens and ‘rhombogens’, whereas rhombogens were reported to produce infusoriform dispersal larvae and occasionally to both produce larvae and revert to the nematogen stage. Observations on laboratory populations of Mesozoa make this distinction untenable. 1885 Geddes in Encycl. Brit. XVIII. 259/1 The embryos are of two kinds, *nematogenic or vermiform, and rhombogenic or infusiform. 1877 Huxley Anat. Inv. Anim. xi. 654 The *nematogenous Dicyema gives rise by an agamogenetic process to new Dicyemas. 1888 Rolleston & Jackson Anim. Life 817 The Nematogenous individual varies somewhat in shape. 1835–6 Owen in Todd's Cycl. Anat. I. 47/2 The difference in the condition of the digestive system between the Acrite and *Nematoneurous classes is still more striking. 1839–47 T. R. Jones ibid. III. 535/1 The Bryozoa‥belong to the Nematoneurose type. 1837 Penny Cycl. VII. 202/1 [The] Cirrhopodes of Cuvier,‥*Nematopodes of De Blainville.