Text-book of comparative anatomy . airs of nephridia, Inwhich show a remarkableagreement with the provi-sional trunk nephridia ofcertain Poluchceta (Nerei*ctiltrifeid, Fig. 159, p. 239).They lie one behind theother in the trunk regionin those segments whichare outwardly indicatedand demarcated by ciliatedrings. The nephridia ofthe Rotatoria (Fig. 161)consist of two looped, andin certain places much con-voluted canals, which runlongitudinally near theintestine; these openinto the cloaca, generallyforming a contractileterminal vesicle. Thelongitudinal canals usuallyhave short accessory branches
Text-book of comparative anatomy . airs of nephridia, Inwhich show a remarkableagreement with the provi-sional trunk nephridia ofcertain Poluchceta (Nerei*ctiltrifeid, Fig. 159, p. 239).They lie one behind theother in the trunk regionin those segments whichare outwardly indicatedand demarcated by ciliatedrings. The nephridia ofthe Rotatoria (Fig. 161)consist of two looped, andin certain places much con-voluted canals, which runlongitudinally near theintestine; these openinto the cloaca, generallyforming a contractileterminal vesicle. Thelongitudinal canals usuallyhave short accessory branches whose ends FIG. 161.—Organisation of Hydatina senta, after Plate., ... j i i -i -i w, Wheel organ ; ni, nephridial ciliated cells; n, nephridia ; ^ClliateCl lODCS, Vioratlle ph, pharynx; md, gastric glands; m, stomach; ds, vit>•!- larium ; l;s, germarium ; rb, outline of the contractile vesicle ; ed, hind-gut; u, uterus ; a, anus ; fd, cement or pedal glands ; It, lateral feeler; ?>i, nerve of the same ; c, advanced organs) seem to be con-structed like the ends ofthe water-vascular systemof the Plat odes, and of the embryonic head nephridia of the •246 COMPARATIVE ANATOMY CHAP. md Annulata. This correspondence indeed is apparent in the whole nephridium. The only organs which can perhaps be pointed to as transformed nephridia in the Chwtognatha are the ovi-ducts and the sperm ducts; these arepaired tubes, the oviducts opening out-wardly at the posterior end of the trunksegment, the sperm ducts in the tailsegment by paired lateral latter are provided with funnel-likeciliated inner apertures. X. Respiratory Organs. In many worms no specific respiratoryorgans are developed. Respiration isperformed by means of the integument,and also often by the walls of the general ciliation of the body in theNemertina is of great assistance for respira-tion in water. In the Hirudinea andmany Oligochceta cutaneous respiration isfacilitated by the prese
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
