Elements of the comparative anatomy Elements of the comparative anatomy of vertebrates elementsofcompar00wied Year: 1886 36 COMPARATIVE AN ATOM V. articulat:on at its base, and thus give rise to a rib (cp. p. 4S). Tin' relations of these parts in Elasmobranehs and Teleostcans is similar to that above described. For the further strengthening of the \vrtebral column so-called 'intercalary pieces' (Figs. 21,22, Ic) appear between the upper and luwer arches in Cartilaginous Ganoids and Elasmobranehs. The vertebral column of Bony Ganoids reaches a much higher stage of development. Paired dorsal an
Elements of the comparative anatomy Elements of the comparative anatomy of vertebrates elementsofcompar00wied Year: 1886 36 COMPARATIVE AN ATOM V. articulat:on at its base, and thus give rise to a rib (cp. p. 4S). Tin' relations of these parts in Elasmobranehs and Teleostcans is similar to that above described. For the further strengthening of the \vrtebral column so-called 'intercalary pieces' (Figs. 21,22, Ic) appear between the upper and luwer arches in Cartilaginous Ganoids and Elasmobranehs. The vertebral column of Bony Ganoids reaches a much higher stage of development. Paired dorsal and ventral cartilages arise above and below the notochord, M' — PORTION OF THE VERTKBRAL COLUMN OF //'A', centra; HF, basal processes ; Oft, upper a relies ; Ps, spinous processes. but in the course of development so extend at the base as to com- pletely surround it. From the dorsal cartilages the upper arcln-- take their origin, and from the ventral the lower, while the car- tilage surrounding the notochord gives rise to the vertebral bodies or centra. The whole vertebral column also becomes strongly ossified (Fig. 24). The notochord is now no longer equal in diameter throughout, but becomes constricted or actually divided Zi f' • Y . //A \ a}- mr. NOTOCHORD. (7, C*1, expanded and constricted portions of notocliord ; //'A', centra; /./, intcr- in the et\veen two contiguous vertebraB (Figs. -~> and '11, (', C1). The same thing takes place in other — ElasmobrancWi and Teleostei — and thus deeply biconcave (amphicoelous) lentra are formed. in' nf I li.' l',..n\ ( !an nil 1, forms a \,< <\ .•\ci-pl i. in to other I'i-lH :\ regard rtebral ix-lumn, inasmuch as definite articulations are liet \vee|| tile \ i •! t c •] ,] ie. A eolna\il\ i< I'oniieil at tlie llill']']' i)i(l of
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