Three elements go to make up the vertebral column in Amphibia, viz. 1. the notochord, 2. the long vertebral centra, 3. intervertebral cartilage which forms the joints between successive centra. The relations which these three elements bear to one another are subject to much variation. The successive stages can be well traced in the Urodela. 1. The first stage is found in larval Urodeles in general and in adult Ichthyoidea, and some Salamandrina. In these forms the notochord persists and retains approximately the same diameter throughout the whole length of the vertebral column. Bony biconcave centra are present and constrict it to a certain extent vertebrally, while intervertebrally there is a development of cartilage. The connection between the bony vertebrae is effected mainly by the expanded notochord. 2. In the next stage, as seen in _Gyrinophilus porphyriticus_, the growth of intervertebral cartilage has caused the almost complete obliteration of the notochord intervertebrally, and its entire disappearance vertebrally, i.e. in the centre of each vertebra. The intervertebral cartilage now forms the main connection between successive vertebrae, and sometimes cases are found whose condition approaches that of definite articulations. Readily recognisable remains of the notochord are still found at each end of the intervertebral constriction. 3. In the third stage differentiation and absorption of the intervertebral cartilage has given rise to definitely articulating opisthocoelous vertebrae. These are found in most adult Salamandrina. * * * * * The transverse processes of the earlier trunk vertebrae are divided into two parts, a dorsal part which meets the tubercular process of the rib and is derived from the neural arch, and a ventral part which meets the capitular process of the rib, and is derived from the ventral or haemal arch. In the caudal vertebrae and often also in the posterior trunk vertebrae the two processes are fused. _Siren_ and _Proteus_, although they possess minute posterior limbs, have no sacral vertebrae, while _Cryptobranchus lateralis_ has two. The caudal vertebrae, except the first, have haemal arches very similar to the neural arches. In Labyrinthodontia the centra of the vertebrae are generally well ossified biconcave discs. In some forms however, like _Euchirosaurus_, the centra are imperfectly ossified, and consist of bony rings traversed by a wide notochordal canal. Each ring is formed of four pieces, a large well-ossified neural arch, a basal piece, and a pair of lateral pieces. Vertebrae of this type are called _rachitomous_.