NEMATOMORPHA  . This zoological

group includes Gordian worms which are found swimming in an undulatory manner or coiling round water-weeds in ponds and puddles, or knotted together in an apparently inextricable coil . They may he several inches in length and are no thicker than a piece of whip-cord . The male is distinguishable from the female by the presence of a fork at the posterior end of the body . The body is covered by a cuticle which is sculptured and the various markings are of systematic importance: it is secreted by a hypodermis which also includes nerve-cells and some gland-cells . In the adult aquatic stage the alimentary canal shows signs of degeneration, and it seems probable that in this stage Gordian worms take no food . The mouth is terminal or subterminal; there is a weak sucking pharynx situated behind the brain, and a long intestine lying along the medio-ventral body-cavity; it ends in a cloaca which receives the vasa deferentia in the male . There is a single unsegmented nerve-cord which runs along the ventral middle line .and enlarges posteriorly into a caudal ganglion and anteriorly in a ganglion, the brain, which is not supra-oesophageal . The peripheral nervous system is minutely described by T, H . Montgomery . There is a median eye on the head . A,a,Female Heterodera schachtii Schmidt, breaking through the epidermis of a root; the head is still embedded in the parenchyma of the root .

B, a, larvae

boring their way into a root; 6, larva of the immobile kind surrounded by the old skin, living as an ectoparasite on the outside of the root . (From Strubell.) B, First motile larva . C, Second immovable parasitic larva casting its skin . D, A female with one half of the body-wall taken away to show the coiling generative organs . a, Boring apparatus . b, Oesophageal bulb . c, Excretory pore . d, Alimentary canal . e, Anus . f, Ovary . E, A male shortly before casting its larval skin . and only in the middle, region of the body are there any. body- cavities, the space within the body being usually filled up with parenchyma .

There are four closed spaces of the nature of body-cavities, two lateral and a dorso-median and a ventro- median . Into the former the ovaries project, though the lumen of the lateral body-cavity is quite shut off from the lumina of the ovaries or uteri . In the adult male the lateral body-cavities are absent . A curious duct with lateral branches termed the supra-intestinal

organ lies above the intestine in the female . There are two series of ovaries extending through a large part of the body and accompanied by two uteri; the latter open by two oviducts which debouch into an atrium which also receives the intestine and a single receptaculum seminis, and is continued back-ward as the cloaca; this opens posteriorly . The ovaries are epithelial sacs which open into the uteri . The paired testes extend through the greater part of the body and end in two vasa deferentia which unite with the intestine to form a cloaca . From Cambridge Natural The eggs are laid in the spring as a rule, History, vol. ii., "Worms," &c., by permission of Mac- and after about a week they give rise to a millan & Co., Ltd . F IG . 3.—Tarsal joint minute, ringed larva with a protrusible of an Ephemerid larva boring apparatus corii,isting of three into which two Gordius chitinous rods . By the aid o; this the larvae, (a,a) have larva makes its way into the soft body penetrated . Magnified. of some insect larva, Ephemerids, Chiro- nomids, or even of Molluscs, and encysts in the muscles or fat body .

The insect, which may have become an imago with the Gordian larva still in it, is then eaten by a carnivorous insect or by a

fish, and the contained Gordian larva becomes elongate and mature in its second host . After a year or more this larva emerges into the water and commences to reproduce . The unexpected occurrence of these worms in pools and puddles, often in great numbers, has given rise to myths about showers of worms . They occasionally make their way into the human stomach with the drinking-water and are vomited; but this is a case of pseudo-parasitism—they are no true parasite of man . There are a considerable number of species divided among the four genera: Gordius, Paragordius, Chordodes and Parachordodes; the last, a genus of Camerano's, is looked upon with some doubt by Montgomery . A free swimming marine form with longitudinal rows of bristles, known as Nectonema A . E . Verrill, may also come here, but at present its life-history is unknown . The Nematomorpha form an isolated group; at first sight they seem to be connected with the Nematoda, but in reality their only common feature is the tubular genitalia opening into a cloaca, and it seems at present363 impossible to connect them with the Annelida . Until more is known it seems wisest to look upon them as an isolated assemblage of animals with no' near affinities to any of the great phyla .