454 HERPETOLOGY. 



of the fish, with the addition of a modified state of pulmonary 

 circulation. We advert thus particularly to these peculiarities, 

 because they present proof so striking of divine contrivance. 



Reptiles have either four limbs, (Plate XII. figs. 1, 4, 6,) two, 

 (see Chirotes or Bipes on the Chart,) or none, (Plate XII. fig. 5 ;) 

 the ribs are sometimes very numerous, (Plate XII. fig. 5,) some- 

 times wanting or merely rudimentary, (Plate XII. fig. 4 ;) in the 

 latter case, the ribs assist greatly in terrestrial locomotion. There 

 is no true distinction between the chest and abdomen, no dia- 

 phragm or muscular expansion, dividing, as in quadrupeds, these 

 two cavities. As the blood is of a low temperature, these ani- 

 mals need neither fur nor feathers for the retention of the vital 

 heat. They are therefore covered either with horny plates, or 

 with scales, or have the skin entirely naked. Their sight is in 

 general extremely acute. On this sense they depend in their 

 pursuit of food, and for their perception of the approach of ene- 

 mies. The senses of taste, smell, and touch, in reptiles are com- 

 paratively feeble. With regard to hearing, considerable varia- 

 tion appears in different groups. In serpents, the sense is very 

 acute, and they evidently derive pleasure from musical notes, a 

 fact well understood by the serpent-charmers of the East. In 

 lizards, also, the sense of hearing appears to be quick ; in tor- 

 toises and in the Amphibians it is probably much more obtuse. In 

 most cases the internal organs of hearing are entirely covered by 

 the scaly investment of the head, or by the naked skin. In liz- 

 ards generally, the tympanic, or drum-like membrane, is stretched 

 over the external orifice of the ear, and is on a level with the 

 scaly covering of the rest of the head ; but in the crocodile, the 

 external orifice, instead of being thus permanently closed, is pro- 

 vided with a firm, movable lid or operculum, by means of which 

 the aperture may be either stopped or kept open. While bask- 

 ing on the margin of a river, or lying there in ambush for prey, 

 the crocodile is able to raise the ear-lid, in order to listen atten- 

 tively to every noise ; but when he dives beneath the water, 

 either for safety or to drown the victim he has seized, the en- 

 trance of water into the auditory cavities is prevented by the 

 firm shutting of the lid, which accurately fits the orifice. 



Reptiles are ordinarily produced from eggs. Many of them 

 exhibit extraordinary fecundity. None of them, unless the 

 Pythons be an exception, ever perform the process of incubation. 

 They bury their eggs in the sand, deposit them in warm places 

 of concealment, or leave them floating in the water exposed to 

 the rays of the sun. In due time the young are hatched. In 

 some Reptiles which produce eggs, as the Viper, the young is 



