Elements of comparative anatomy (1878) Elements of comparative anatomy elementsofcompar00gege Year: 1878 cs~ Fig. 222. Diagram of the changes produced in the notochord by the skeletogenous layer (longitudinal sections), c Chorda, cs Chordal sheath, s Skeletogenous layer. v Bodie3 of the vertebra). iv Intervertebral portion. g Intervertebral joint. A The chordal tube, when all its parts are equally well developed (Fishes). B Interver- tebral growth of the chorda. Formation of amphicoelous vertebras (Fishes). 0 In- tervertebral constriction of the chorda by cartilage ; while the rest of the cho
Elements of comparative anatomy (1878) Elements of comparative anatomy elementsofcompar00gege Year: 1878 cs~ Fig. 222. Diagram of the changes produced in the notochord by the skeletogenous layer (longitudinal sections), c Chorda, cs Chordal sheath, s Skeletogenous layer. v Bodie3 of the vertebra). iv Intervertebral portion. g Intervertebral joint. A The chordal tube, when all its parts are equally well developed (Fishes). B Interver- tebral growth of the chorda. Formation of amphicoelous vertebras (Fishes). 0 In- tervertebral constriction of the chorda by cartilage ; while the rest of the chorda is retained in the vertebrae (Amphibia). D Intervertebral constriction of the chorda (Reptilia, Aves). E Vertebral constriction of the chorda, where part of tho interver- tebral portion is retained (Mammalia). The cartilage sometimes forms a cylindrical tube, in which the vertebras are merely represented by the arches and circular parts of the skeletogenous sheath. The notochord is sometimes developed between the vertebras (Fig. 222, B), and retains its earlier size at tho points where the vertebra (y) and arches were first laid down around it. This arrangement gives rise to biconcave (amphicoelous) vertebras (B), the depressions in which are filled up by the intervertebral chord. This is the way in which the vertebras of nearly all other fishes are formed. § 329. In the Gano'i'dei the vertebral column, when simplest in organisa- tion, resembles that of the Selachii. Just as in the Selachii and
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