. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. VEBTEBRAL COLU^IX 35 Fig. -Diagrams illdsteatixg the Development of the Notochokdal Sheaths and Vertebral Column. B. C. -Early stage, showing notoehordal cells (hc) and primary sheath (nh^), as well as the mesoblastio skeletogenoiis layer {). -Later stage, in which the central notoehordal cells (nr) have become vacuolated and the peripheral cells have given to the " notoehordal epithe- limn" (rec. ep.) from which the fibrillar secondary sheath (sW) is derived
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. VEBTEBRAL COLU^IX 35 Fig. -Diagrams illdsteatixg the Development of the Notochokdal Sheaths and Vertebral Column. B. C. -Early stage, showing notoehordal cells (hc) and primary sheath (nh^), as well as the mesoblastio skeletogenoiis layer {). -Later stage, in which the central notoehordal cells (nr) have become vacuolated and the peripheral cells have given to the " notoehordal epithe- limn" (rec. ep.) from which the fibrillar secondary sheath (sW) is derived : paired dorsal and ventral cartilages {, ) have arisen in the skeletogenoiis layer. Cartilage cells have passed through the primary sheath, and are invading the secondary sheath (Cartilaginous Ganoids, Holocephali, Dipnoi, Elasmo- branohii : in the last named chorda-centra are thus formed). D.—The cartilages are growing round the notochord, outside its sheaths, which gradually become reduced : thus arch-centra are formed (Bony Ganoids, Teleostei, Amphibia, Amniota). A—D represent the caudal region. E.—A later stage in the development of a pre-caudal vertebra. The notochord (nc) has become constricted, and the cartilages have united into a single mass and have given rise to a centrum (c), neural arch (), neural spine {n. sp), transverse processes () and articular processes (art); D 2. 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 Wiedersheim, Robert, 1848-1923; Parker, William Newton, 1857-1923. London, Macmillan
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
