GENERAL ANATOMY 87 



notion of its being a poison -organ. The whole structure is 

 possibly an offshoot of the naso-lacrymal duct. 



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 entiiely 

 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 ChtJionerpeton, 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 IcJithyophis, p. 91, and Hypogeophis, 

 p. 92. The female is fertilised internally, copulation taking place 

 hj 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 



