The Cambridge natural history . h the Dibranchiate Cephalopods (Argonauta, Octopus,Loligo, etc.), the Zygobranchiate Prosobranchs {Pissurella, Hali-otis), and all Pelecypoda. In the Amphineura {Chiton, etc.) thereare two auricles corresponding to the two sets of multiplebranchiae. In the case of the Tetrabranchiate Cephalopods{Nautilus) there are four auricles corresponding to each of thefour branchiae. Compare Fig. 79, A, B, C, D, E. On the other hand, when the branchia is single, or when bothbranchiae are on the same side, and one is aborted and functionless,the auricle is single too, and on
The Cambridge natural history . h the Dibranchiate Cephalopods (Argonauta, Octopus,Loligo, etc.), the Zygobranchiate Prosobranchs {Pissurella, Hali-otis), and all Pelecypoda. In the Amphineura {Chiton, etc.) thereare two auricles corresponding to the two sets of multiplebranchiae. In the case of the Tetrabranchiate Cephalopods{Nautilus) there are four auricles corresponding to each of thefour branchiae. Compare Fig. 79, A, B, C, D, E. On the other hand, when the branchia is single, or when bothbranchiae are on the same side, and one is aborted and functionless,the auricle is single too, and on the same side as the is the case with the Tectibranchiate Opisthobranchs {Philine,Scaphander, etc.), all the Pectinibranchiate Prosobranchs (Eachi-glossa, Taenioglossa, and Ptenoglossa), and the other Azygobran-^ Pelseneer, Comptes Rendus, cvi. p. 1029. CIRCULATORY SYSTEM 169 cliiate rrosol) (Trochidae, Neritidae, etc.). In the last casethe right auricle exists, as well as the left, but is simply a closed. Fig. 79.—Diagram illustrating the relations between branchiae, heart, and aorta in theMollusca : A, In Chiton ; B, Pelecypoda; C, Dibranchiate Cephalopoda; D, Tetra-branchiate Cephalopoda ; E, Prosobrauchiata Zygobranchiata ; F, ProsobrauchiataAzygobranchiata ; G, Prosobranchiata Monotocardia ; H, Opisthobranchiata Tecti-branchiata : 1, Ventricle ; 2, Auricle ; 3, Aorta ; 3a, Cephalic aorta ; 3b, Visceralaorta ; 3c, Posterior aorta. (From A. Lang.) sac, the coalescing of the two gills on the left side having thrownall the w^ork upon the left auricle. Compare Fig. 79, F, G, H. Circulatory System. All Mollusca, without exception, possess a circulatory systemof more or less complexity. Tlie centre of the system is the heart,which receives the aerated blood from the breathing organs, andpropels it to every part of the body. In the Scaphopoda alonethere appears to be no distinct heart. The heart may consist simply of a single amnele and vent-ricle, and an
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
