C&CILIANS. 



453 



States and Pseudobranchus striatus of Georgia. Both these lowly creatures 

 have long eel-like bodies, external gills, and a small pair of front legs. The 



hind - legs are, 

 however, total- 

 ly wanting, and 



Fig. 16. TWO-LEGGED SALAMANDER (Siren lacertina). 



Family 

 Sirenidce. 

 there are no 

 teeth in the margins of the jaws. 

 In the species first named- 

 which may measure nearly 

 twenty inches in length there 

 are three pairs of gill-openings 

 on the sides of the neck, and 

 each of the fore-feet is fur- 

 nished with four toes. From 

 this genus Pseudobranchus is dis- 

 tinguished by the presence of 

 only a single pair of gill-aper- 

 tures, and the reduction of the 

 front toes to three. These sala- 

 manders frequent damp situa- 



tions and pools, and occasionally ascend the aerial roots or stems of trees. 

 They are carnivorous in their habits, and are able to breathe either by their 

 gills or their lungs. During the colder months of the year they hibernate. 



ORDER III. APODA. 



dECILIANS. 



THE third and last order of Amphibia is represented by the blind, burrow- 

 ing creatures commonly known as caecilians. In appearance they are so 

 worm-like that by the non-scientific observer they might readily be mistaken 

 for Invertebrates. In the adult state they show no trace of limbs ; but bud- 

 like remnants of hind-legs have been detected in the embryos of Ichthyophis 

 ylutinosus. This clearly shows that they are a degraded form, but whether 

 they are descended as has been considered the case from the tailed 

 amphibians may, perhaps, be doubtful, seeing that they differ from that 

 group in an important feature connected with their reproduction. They 

 have either a rudimental tail or none at all, and they are further character- 

 ised by certain structural peculiarities in the osteology of the skull. The 

 eyes are generally deeply buried beneath the skin, or placed beneath the 

 bones of the skull, and in certain members of the group overlapping scales 

 are concealed deep down in the skin. The head is provided with a tentacle, 

 which may be capable of protrusion and retraction. Csecilians present a very 

 remarkable geographical distribution, being restricted to South and Central 

 America (with the West Indies), Africa south of the Sahara, the Seychelles, 

 and the Oriental countries. Their absence from Madagascar, coupled with 

 their existence in the Seychelles, is a very noteworthy circumstance, and 

 seems to indicate a connection between those islands and either Africa or 

 India after Madagascar was insulated. The adults burrow in moist earth, 



