SKELETON. 



but also as a respiratory organ, is as 

 a rule naked arid slimy. The Ccetiliidce 

 alone possess thickened cutaneous 

 rings, in which scales are imbedded. 

 The sense organs of the lateral line 

 (tig. 620) also are present in the 

 aquatic forms, especially in the larval 

 condition. Glands and pigments are 

 very generally present in the integu- 

 ment. The former often secrete 

 strongly smelling and caustic juices, 

 which act as poisons on other or- 

 ganisms (parotid glands, as well as 

 glands on the sides and posterior 

 extremities). The various colourings 

 of the skin are principally due to 

 branched pigment cells of the cutis. 

 The change of colour in the Frogs 

 a phenomenon which has been known 

 for some time is caused by changes 

 in the form of these cells. 



Skeleton. -Although a notochord 

 may persist (Cosciliidce, Proteus], yet 

 bony, at tirst biconcave vertebrae,* are 

 always developed, and are separated 

 by intervertebral cartilages. In the 

 Salamandrina the cartilage in the 

 intervertebral regions grows con- 

 siderably and gradually supplants the 

 notochord, the remains of which be- 

 come cartilaginous. As the result 

 of further differentiation of the inter- 

 vertebral cartilages, the rudiments of 

 an articular head and an articular 

 cup are developed, which, however, 

 are only completely separated in the 

 Batrachians provided with proccelous 



177 



R 



* Compare especially < '. Gegenbaur, " Un- 

 tersuchungen zur vergleichenden Anatomie 

 dcr \Virbdsaiiir bei Amphibian und Repti- 

 lien," Leipzig, LSi',2. 



VOL. II. 



FIG. 621. Skeleton of Menopoma aJ- 

 leghanitnse. Ocl, Exoccipital ; P, pari- 

 etal ; F, frontal ; Ty, tympanic ; Pe, 

 petrous (prootic); MX, maxilla; Jin.r, 

 \ iv; i 'maxilla ; N, nasal; T'o, vomer; Et, 

 girdle bone (sphen-ethmoid) ; Ft, 

 pterygoid ; Sc, pectoral arch; Jl, pel- 

 vic arch ; 8, sacral vertebra; R, ribs. 

 I, hyoid aparatus (remains of liyni.l 

 (Zl) and branchial arches (El). 



12 



