The majority of Vertebrata are oviparous. Mammalia except Proto-theria are viviparous, and instances of viviparity occur among Lacertilia, Ophidia, Urodele Amphibia, Teleostei and Elasmobranchii.

There are two divisions of Vertebrata, the Amniota and the Anamniotas. Icthyopsida.

Lehrbuch der Vergleich. Anat. der Wirbelthiere, Wiedersheim, Jena, 1883. Anatomy of vertebrated animals, Huxley, London, 1871. Anatomy of Vertebrates, Owen, 3 vols. London, 1866-68.

Morphology of skull, Parker and Bettany, London, 1877.

Pineal gland, Ahlborn, Z. W. Z. xl. 1884; and eye, De Graaf, Z. A. ix. 1886; Spencer, Nature, xxxiv. 1886.

Cranial nerves, Milnes, Marshall, and Spencer, Q. J. M. xxi. 1881; cf. Beard, 'Branchial sense-organs,' etc, Q. J. M. xxvi. with lit. p. 148-151.

Mucous membrane of nose in Pisces and Amphibia, Blaue, Arch. f. Anat. u. Physiol., Anat. Abth., 1884. Phylogeny of Vertebrate eye, Dohrn, Mitth. Zool. Stat. Naples, vi. 1885. Ear, Retzius, Gehororgan der Wirbelthiere, Stockholm, i.

1881; ii. 1884; (abstracts in Biol. Centralblatt, ii. 1882-85; v. 1885-86). Middle and external ear, Moldenhauer, M. J. iii. 1878. Bones of Ear in the Mammalia, W. K. Parker, 'Mammalian Descent,' Hunterian Lectures, 1884, p. 39.

Comparative anatomy of Tongue, Ludwig Ferdinand, Konigler Prinz von Bayern, Miinchen, 1884.

Thymus and Thyroid, development, Fischelis, A. M. A. xxv. 1885; cf. Dohrn, Mitth. Zool. Stat. Naples, vi. 1885.

Blood corpuscles of Vertebrata, Gulliver, P. Z. S. 1875.

Cloaca, etc, Spoof, Embryol. u. Vergleich. Anat. der Kloake u. der Uro-genital-system bei den hoheren Wirbelthieren, Helsingfors, 1883.

Development of organs in general, Balfour, Comparative Embryology, ii. 1881, Chapters on Organogeny; Foster and Balfour, 'Embryology of Chick,' ed. 2, by Sedgwick and Heape, London, 1883.

Amniota s. Allantoidea s. Abranchiata.

The embryo is provided with the two foetal envelopes known as the amnion and allantois. Branchiae are never developed.

Three classes are included in this division of Vertebrata, the Mammalia, Aves and Reptilia. The two latter are very closely connected in descent, and may be grouped together as Sauropsida.