. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 324 tlic primary arterial arch, corresponding with the anterior or hyoid one, developes either a simple (iiniscrial) gill, or a plexiform, plu- mose, rudiment of a gill, or both, or neither. In the Lepidostcus this arch retains its primitive connection witli the extremity of the branchi-arterial trunk, and developes on each side a small uuiserial pectinated gill, fig. , 1, from the membrane clothing the inner surface of the cerato-hyoid and preopercular bones: the vein or effe- rent vessel, e, of this gill goes to a
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 324 tlic primary arterial arch, corresponding with the anterior or hyoid one, developes either a simple (iiniscrial) gill, or a plexiform, plu- mose, rudiment of a gill, or both, or neither. In the Lepidostcus this arch retains its primitive connection witli the extremity of the branchi-arterial trunk, and developes on each side a small uuiserial pectinated gill, fig. , 1, from the membrane clothing the inner surface of the cerato-hyoid and preopercular bones: the vein or effe- rent vessel, e, of this gill goes to a smaller pectinated organ, ib. R, consisting like- wise of one series of vascular filaments, whicli agrees witli the ' pscudoliranchia ' of other fislies in being supjilied with arterial blood. In the Sturgeon, the Lepidosiren, and tlie Plagiostomes the representative of the primary vascular arch has bec(.)me, by partial bifurcation of the branchi-arterial trunk, a secondary branch, sent otf by the artery of tlie first branchial arch: but it nevertlielcss developes a simple gill, of one series of filaments in the Lepidosiren, fig. 324, i, and of tlie anterior scries of lamella; in the first gill-bag of the Plagiostomes : and this series is attached, like the opercular gill of tlie Lepidostcus and Sturgeon, to the membrane supported by the hyoid arch. In most Osseous Fishes we recognise the reduced homologue of the anterior primary vascular arch in that vessel, fig. 321, e, which is continued from the venous or refluent division of the second jii'imary vascular arch ; not, as in the foregoing fishes, from tlie ar- terial division of that arch, or from tlie liranchial trunk. Tlie vessel in question carries, therefore, arterial blood: it manifests its primitive character by returning into the circulus aorticus, as at <â , fig. 321, but now receives blood from it, and is called ' arteria. . 1-. Please note that these images are extracted from scanned page images that m
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