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Show 684 MR. J. GRAHAM KERR ON THE [June 18, (4) The traces of metamerism exhibited by the heart in some forms, there existing several pairs (four in Chiton magni-ficus) of auriculo-ventricular openings. (5) General relations of ccelom, nephridia, &c. (6) Eggs developed within follicles. ;Fig. 6. Diagram showing the relationships of the coelom and nephridia in Amphineura and Cephalopoda. A, Chcetoderma; B, Chiton; C, Nautilus; D, Sepia. gc, genital division of the ccelom ; pc, pericardiac division of the coelom ; gn, nephridia of genital segment; pn, nephridia of pericardiac segment; ks, kidney-sacs in Nautilus; in Sepia the two posterior kidney-sacs are seen still in communication with the rest of the nephridia. In regard to (5), fig. 6 indicates diagrammatically the relationships of the parts concerned. In the case of Chiton (B) two coelomic chambers are shown, one lying in front of the other-the genital coelom and the pericardium. The pericardium communicates with the exterior by a pair of functional nephridia; the genital coelom by the pair of genital ducts which from their relations can hardly be otherwise than morphologically a pair of nephridia too. In Chcetoderma (A), a less primitive animal, a less primitive arrangement has been developed: the genital division of the coelom has developed a communication with the pericardium through which the genital products pass-and it has lost its original genital ducts. |