The skin is most remarkable. In the ripe embryo the epidermis passes smoothly over the surface. Beneath follow two layers of soft cutaneous connective tissue, bound together by transverse or vertical lamellae, so that ring-shaped compartments are formed, and in these are embedded slime-glands. In the adult each compartment is modified into an anterior glandular belt and a posterior space, from the bottom of which grow several scales. The number of cutaneous rings agrees originally with that of the vertebrae; but later, and especially in the hinder portion of the trunk, each ring breaks up into two or more secondary segments, and these no longer agree with those of the skeleton. Each scale is beset with numerous smaller scales which consist of hardened cell-secretions infiltrated with calcareous matter. The whole scale is consequently an entirely mesodermal product of the deeper layers of the cutis. The usual statement that the skin forms imbricating lamellae, on the inner side of which appear the scales, is wrong. The "lamellae" can be lifted up only after the general epidermal sheath has been broken artificially in the constrictions between the rings. No scales exist in the Indian genus _Gegenophis_ and in the American _Siphonops_, _Typhlonectes_, and _Chthonerpeton_, a secondary loss which does not indicate relationship. The scales develop late in embryonic life, and they are reasonably looked upon as inheritances from the Stegocephali. The glands either produce slime, whose function seems to be the keeping clean of the surface of the body, or they are squirt-glands. The latter kind are also numerous and are filled with a fluid which is squeezed out by muscular contraction, and seems to be poisonous, as it causes sneezing to those who handle or dissect fresh specimens. The Coecilians live in moist ground and lead a burrowing life. Their developmental history has only recently been studied, and in but a few species, see _Ichthyophis_, p. 91, and _Hypogeophis_, p. 92. The female is fertilised internally, copulation taking place by means of eversion of the cloacal walls in the shape of a tube. The spermatozoa possess an undulating membrane; the eggs undergo meroblastic division and the embryos have three pairs of long external gills. Some are viviparous. The snake-like, limbless shape of the body (Fig. 15) is, as in {88}snakes, correlated with an asymmetrical development of the lungs; the left is reduced, while the right is drawn out into a long cylindrical sac. The liver is likewise very long, and partly constricted into a great number of lobes. Owing to the great reduction of the ribs progression is effected in an almost earthworm-like fashion by the peristaltic motion of the skin, assisted by its numerous ring-shaped constrictions.