. Elements of Comparative Anatomy. 470 COMPAEATIVE ANATOMY. tlie hinder ones {IV V) are united to a single piece (a), and are always degenerated, both in size and number. The last pair of all {VI), which merely consists of a single piece on either side, carries no gills; in the fifth arch also there are often gill-lamellte on one side only; in. Fig. 256. Hyoid and branchial arches of Perca fhiviatilis. I—FT Arches; the first (I) is converted into an organ for the support of the hyoid; the next four (71—V) are branchial arches, and the last {VI) forms the infra-pharyngeal bone, a h c d Segments
. Elements of Comparative Anatomy. 470 COMPAEATIVE ANATOMY. tlie hinder ones {IV V) are united to a single piece (a), and are always degenerated, both in size and number. The last pair of all {VI), which merely consists of a single piece on either side, carries no gills; in the fifth arch also there are often gill-lamellte on one side only; in. Fig. 256. Hyoid and branchial arches of Perca fhiviatilis. I—FT Arches; the first (I) is converted into an organ for the support of the hyoid; the next four (71—V) are branchial arches, and the last {VI) forms the infra-pharyngeal bone, a h c d Segments of the arches. The uppermost piece (d) forms the supra-pharyngeal bones. r Branchiostegal rays, f g h Copula (after Cuvier). the last, however, dental structures are more completely developed, so that this piece is often capable of functioning as a masticatory organ. In the Pharyngognathi the rudiments of the last arch, on either side, are fused into one piece. We meet with other modifications of the posterior branchial arches in the Labyrinthobranchiata, and in various Clupeidee; these are due to the conversion of various segments of the arches into the "walls of spaces into which water is received. Just as the hyoid arch of the Selachii is provided with cartila- ginous appendages, so also the succeeding arches are beset with cartilaginous rays which support the walls of the branchial pouch. Even these structures are rudimentary in the Ganoidei and Teleostei, where they form fine cartilaginous lamellge, placed between the I'ows of the branchial folds. § 355. The branchial skeleton of the Amjjhibia is considerably reduced) such forms as undergo a metamorphosis have the gills reduced, and. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gegenbaur, C. (Carl). London : Macmillan
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