HAPLODRILI (so called by Lankester)  , often called Archiannelida (Hatschek), the name provisionally given to a number of A, Polygordius neapolitanus . (From Fraipont.) B, Transverse section of Polygordius . (From Fraipont.) C, Trochophore of Polygordius. and D, later stage of the same, showing the development of the trunk . (From Hatschek.) E, Dorsal view of Dinophilus taeniatus . F, Male apparatus of the sa ne (From Harmer.) a, Anus . ap, Apical organ . c, Coelom . c.o, Ciliated pit . c.t, Cuticle . d.v, Dorsal vessel . e, Eye . ep, Epidermis .

g,f, Genital

funnel . h, "Head kidney," with second nephridium just below it . i, Intestine . Lm, Longitudinal muscles . m, Mouth . m.o, Muscular pharyngeal organ. m.p, Male pore . n, Nephridium . o.m, Oblique muscles . ov, Ovary . p, Penis . pr, Prototroch . pt, Prostomial tentacle .

sp, Sperm-

sac . spd, Sperm-duct . si, Stomach . t, Testes . tr, Trunk segment . tt, Telotroch . v.n, Ventral nerve cord . v.v, Ventral vessel . interesting lowly-organized marine worms, whose affinities are very doubtful (see CHAETOPODA) . Polygordius and Protodrilus Whatever may be the conclusion as to the position of Dinophilus and Histriodrilus, it seems only reasonable to suppose that Polygordius and Protodrilus, so far from representing a stage in the phylogeny of the Annelida before setae were developed, have lost the setae, which -are already in a reduced state in Saccocirrus . AUTHORITIEs.—Hatschek, " Studien z . Entw. der Anneliden," Arb .

Zool . Inst . Wien, vol. i., 1878; " Protodrilus," ibid. vol. iii . (1881); Fraipont, "Le Genre Polygordius,"

Fauna u . Flora d . Golfes v . Neapel., xiv., 1887; Weldon, " Dinophilus gigas," Quart . Journ . Micr . Sci. vol. xxvii., 1886; Harmer, " Dinophilus," Journ . Mar . Biol .

N.S. vol. i., 1889; Schimkewitsch, " Entwickl.

des Dinophilus," Zeit. f. wiss . Zool. vol. lix., 1895; Korschelt, " ~} V ber Bau u . Entw. des Dinophilus," Zeit. f. wiss . Zool. vol. xxxvii., 1882; Foettinger, " Histriobdella," Arch . Biol. vol. v., 1884; Goodrich, " On Saccocirrus," Quart . Journ . Micr . Sci. vol. xliv., 1901 . (E . S .