. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. LIMBS 103 formed in all the Fishes proper and in Dipnoans; these, which may conveniently be distinguished as " pterygiophores," may unite to form a hasipterygium, and in bony Fishes they become ex- tensively ossified: they frequently come into secondary con- nection with the vertebral column {, by means of the so-called " interspinous bones" of Teleostei). The peripheral part of the fin is supported by dermal rays, which may consist of numerous delicate horny fibres [, Marsipobranchs, Elasmo
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. LIMBS 103 formed in all the Fishes proper and in Dipnoans; these, which may conveniently be distinguished as " pterygiophores," may unite to form a hasipterygium, and in bony Fishes they become ex- tensively ossified: they frequently come into secondary con- nection with the vertebral column {, by means of the so-called " interspinous bones" of Teleostei). The peripheral part of the fin is supported by dermal rays, which may consist of numerous delicate horny fibres [, Marsipobranchs, Elasmobranchs, Cartilag- inous Ganoids, Dipnoans), or of hony rods, entire or jointed, often cleft at the base, and not preformed in cartilage (Teleosts, Bony Ganoids). Median fins are also present in the Amphibia, in which they may persist throughout life {, Perennibranchiata), or may only. Fli:. 81.— SHOWINfl (A) THE UNDIFFERENTIATED CONDITION OF THE Paired and Unpaired Fins in the Embryo, and (B) the manner in WHICH THE Permanent Fins are Formed from the Continuous Folds. IJ, dorsal fin-fold ; S, S, lateral folds, which unite together at kS^ to form the ventral fold ; EF, FF, dorsal fins ; SF, tail-fin ; AF, anal fin ; BrF, pectoral fin; BF, pelvic fin ; An, anus. occur in the larval stage and occasionally also during the breeding season { Newt). They have the form of a continuous in- tegumentary fold extending round the tail and along the back for a greater or less distance, but enclose no skeletal elements. Amongst Reptiles, median fins were present in Ichthyosaurus, and these are comparable to the dorsal fins occurring in the Cetacea amongst Mammals: in both cases they must be looked upon as structures acquired secondarily in connection with an aquatic existence. B. Paired Fins or Iiimbs. Embryological researches have shown tha,t late red Jin-folds must have exiisted in the ancestors of Vertebrates in addition to the. Please note that these images are extracte
Size: 2162px × 1156px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
