. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. Gill Sac â Outer Duct from Sac Common Opening of Branchial Ducts Fig. 321. Diagrams of the heads of (a) Bdellostoma and (b) Myxine. Dorsal views partly dissected to show arrangement of gills. (After Dean.) 4. Elasmobranch and Holocephalan Gills Gills of elasmobranch fishes are lateral in position in sharks and dog- fishes but ventral in the flattened skates and rays. They open independently to the outside and are separated from each other not only by skele
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. Gill Sac â Outer Duct from Sac Common Opening of Branchial Ducts Fig. 321. Diagrams of the heads of (a) Bdellostoma and (b) Myxine. Dorsal views partly dissected to show arrangement of gills. (After Dean.) 4. Elasmobranch and Holocephalan Gills Gills of elasmobranch fishes are lateral in position in sharks and dog- fishes but ventral in the flattened skates and rays. They open independently to the outside and are separated from each other not only by skeletal gill arches of cartilage, but also by primitive partitions attached to these arches, called branchial septa, on either side of which is located a set of filaments, or demibranch. A septum and its two demibranchs together make up a gill, or holobranch. Along the inner margins of the gill arches are finger- like projections, the gill rakers, which not only keep food from entering the slits but also aid in directing it along the straight and narrow esophageal path in which it should go (Fig. 322a). The most anterior pair of the pharyngeal portholes in elasmobranchs, between the mandibular and the hyoid arches, develops into the spiracles,. 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 Walter, Herbert Eugene, b. 1867; Sayles, Leonard Perkins, 1902-. New York : Macmillan Co.
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