SKELETON. 



out also as a respiratory organ, is as 

 a rule naked and slimy. The Coeciliidce 

 alone possess thickened cutaneous 

 rings, in which scales are imbedded. 

 The sense organs of the lateral line 

 (fig. 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 knowTi 

 for some time is caused by changes 

 in the form of these cells. 



Skeleton. Although a notochord 

 may persist (Gveciliidce, Proteus), yet 

 bony, at first 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 F ?\ 621 '~ Ske i eton of Men P nma a - 



. leghanitnse. Ocl, Exoccipital ; P, pari- 



BatrachiailS provided with prOCO3lous etal; F, frontal; Ty, tympanic; Pe, 



petrous (prootic); MX, maxilla; Jmx, 

 praemaxilla ; 2V, nasal ; Vo, vomer ; Et, 



* Compare especially C. Gegenbaur, " Un- gipdle bon f ( s P hen -etnmoid) . pt, 

 tersuchungen zur vergleichenden Anatomic P ter ^ ld '/ c P ectoral arch ; Ji > pel- 

 dcr Wirbelsaiile bei Amphibian und Repti- I 10 ," 1 * J *' sacral 7 ertebra ; * ribs ' 

 lien," Leipzig, 1862. J, hyoid aparatus (remains of hyoid 



(Zb) and branchial arches (Kb). 

 VOL. II. 12 



