. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. CLASSIFICATION OF VERTEBRATES. Tthe orbit and nostril. The caecilians are tropical, occuring in -South America, Africa, and Ceylon, where they burrow in the earth, preying upon small invertebrates. The eyes, in consequence of this life, are hidden under the skin. Little is known of the development, except of the Cey- lonese species, Iclithyopliis gliitinosus, in which the larva has three pairs of pectin- ate external gills. In the larval Typhlo- nectes the gills are saccular. Other genera are Ccecilia, Rhinotreiiia, and Hypo
. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. CLASSIFICATION OF VERTEBRATES. Tthe orbit and nostril. The caecilians are tropical, occuring in -South America, Africa, and Ceylon, where they burrow in the earth, preying upon small invertebrates. The eyes, in consequence of this life, are hidden under the skin. Little is known of the development, except of the Cey- lonese species, Iclithyopliis gliitinosus, in which the larva has three pairs of pectin- ate external gills. In the larval Typhlo- nectes the gills are saccular. Other genera are Ccecilia, Rhinotreiiia, and Hypogeophis. No fossil species are known, but the dis- tribution as well as the characters of the skeleton point to a great ancestry for the group. Within recent years it has been supposed to be related to Ampliiinna, but this is clearly not the case. The aisto- poda (p. 283) suggest themselves in this Fig. 287. Tentacle of 'Cacilia oxyiira^ after Wiedersheim. do, duct â of orbital gland; a?/, duct ⢠of tentacular gland; i", eye; m^ mouth of ten- tacle; ng, nasal gland; j>g, orbital gland; r, re- tractor of tentactle; tg, tentacular gland. GRADE II. A^IXIOTA (ALLAN- TOIDEA). Vertebrates with well-developed amnion and allantois ; no gills, no lateral line sys- tem, and no rental portal system in the adult. The amniotes derive their name from the existence during foetal life of a peculiar envelope â the amnion. This consists of folds of the somatopleure (head, tail, and lateral folds) which :grow upwards on all sides of the embryo, meeting and fusing above the back, so that the embryo is enclosed in a cavity bounded by double walls, that nearest the embryo being the amnion, the other being the chorion. The amnotic cavity is filled with an amniotic fluid. Both amnion and chorion are composed of ectoderm and the somatic mesothelium of the lateral plates, and the space between them is an extension of the -coelom. With growth, the amniotic structures become conn
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