REPTILES. 335 



and generally large, and this organ has sometimes the form of 

 simple sacs, scarcely cellular. They are provided with a tracheal 

 artery and larynx, although all have not the faculty of uttering 

 sounds. 



No species of reptile is possessed of true fleshy lips. Some, as 

 the Tortoises, have a horny bill like the parrot ; others have 

 teeth of various forms, not serving, however, in general for the 

 maceration of food, but for retaining their prey; while others, as 

 certain serpents, have hollow fangs, which are erected when the 

 animal opens its mouth to bite, and which insert an active poi- 

 son into the wound made by these teeth. Reptiles have but one 

 opening for rejected solid and fluid matters, and for the organs 

 of generation. 



The females have a double ovary and two oviducts, and, though 

 oviparous, none of the species hatch their eggs. Those which 

 couple deposit eggs covered with a hard envelope ; and the 

 eggs of those species which do not are soft and glairy. The 

 greater part abandon their eggs after having deposited them in 

 a convenient place ; though some species carry them about with 

 them. The young on quitting the ova appear sometimes in 

 the form which they preserve through life ; but in other cases 

 they are at this period of their existence organized like fishes, 

 are not fully developed till after a certain period, and undergo 

 a complete metamorphosis. Such are the tadpoles of the frog. 



Many species of this class are used as articles of foodnn dif- 

 ferent countries. The use of others in the economy of nature 

 is apparent, in limiting the excessive reproduction of in sects and 

 worms ; while they themselves, on the other hand, form the 

 principal food of some families of birds. The poisonous spe- 

 cies are not very numerous, and their range is daily diminish- 

 ing as cultivation and population increase. 



According to the arrangement of Reptiles by M. Brogniart, 

 and followed by M. Cuvier, founded upon their organization, 

 and which is adopted in the following summary, they are di- 

 vided, as noticed above, into four orders, viz. CHELONIAN REP- 

 TILES or Tortoises ; SAURIAN REPTILES or Lizards ; OPHI- 

 DIAN REPTILES or Serpents ; and BATRACHIAN REPTILES 

 or Frogs. 



