The movements of the Gastrotricha are very elegant, recalling those of the long-necked Ciliate Infusoria, like _Amphileptus, Lacrymaria_, etc., with the characteristic exception that they always swim forwards; the grace of their movements being due to the bending of the head and neck on the body. Those which are provided with long motile bristles like _Dasydetes_, alternate their gliding with leaps, like the springing Rotifers. The Gastrotricha are divided into two sub-Orders—EUICHTHYDINA, with two pedal appendages, containing the genera _Ichthydium_ Ehr., _Lepidoderma_ Zel., _Chaetonotus_ Ehr., and _Chaetura_ Metsch.; and the APODINA, with no pedal appendages, comprising _Dasydetes_ G. and _Gossea_ Zel. Their geographical distribution, like that of most microscopic fresh-water organisms, is cosmopolitan. Few observers have enumerated the members of this group; of their extra-temperate occurrence we have only the single observations of Ehrenberg, Schmarda, and Voeltzkow for Nubia, Ceylon, and Madagascar respectively. Of the thirty-two species described, twelve are recorded by A. C. Stokes from Maine and New Jersey only, besides five others that occur also in Europe. In Europe nineteen species are recorded, one of which, _Ichthydium podura_, has also been found in Nubia and Ceylon. One species, _Chaetonotus tabulatus_ Schmarda, has been recorded by its author from Colombia (in South America). As of the nineteen European species only seven have been recorded as British, we may expect to find that careful study will well repay the student in these islands. The AFFINITIES of this group are probably with the Turbellarians and the Nematodes; they differ from the former in the highly developed alimentary canal, and from the latter in the possession of the ciliated ventral bands and wreath. The general chitinisation of the skin, the primitive body-cavity, the character of the alimentary canal, the ventral opening of the renal canals far in front of the anus are characters shared by the Nematodes, many of which possess bristles like this group. But their affinity must be rather to some hypothetical ancestral group than to any living Nematodes, which are destitute {236}of cilia. To the Rotifers the affinity, dwelt on by Zelinka, is less close. KINORHYNCHA. This Class and Order comprises but one genus, _Echinoderes_ (Fig. 120), founded in 1851 by Dujardin.[289] Reinhard's monograph[290] is the generally accepted authority on this subject, and contains a full bibliography, with diagnoses of the individual species, eighteen in number. [Illustration: FIG. 120.—_Echinoderes dujardinii_ (?), drawn from a preserved specimen taken at Worthing. × about 210. _b_, Bristle; _c.s_, caudal spine; _ph_, pharynx; _s_ and _s'_, the spines on the two segments of the proboscis; _s.g_, salivary glands; _st_, stomach.]