CHAPTER FORTY-SEVEN 



Reptiles dis- 

 tinguished 

 from 

 amphibians 



Characters 



ofReptilia 



REPTILES 



1. MODERN reptiles include the lizards, snakes, croc- 

 odiles, and tortoises. In the popular mind they are 

 confused with the amphibians, but they represent a very 

 distinct group, much more perfectly adapted to terres- 

 trial life. Whereas the amphibians lay soft eggs in the 

 water, and pass at least their early stages in that 

 medium, the reptilian type is able to produce hard- 

 shelled eggs, which are laid on land, often in the driest 

 situations. It is the development of an egg shell which 

 makes terrestrial life possible, and enables the animals 

 to exist far from water. The only practicable alter- 

 native to this arrangement is viviparity ; and it is inter- 

 esting to see that the birds and mammals, each diverging 

 from a primitive reptilian group, have adopted the two 

 possible methods, the birds continuing the egg-laying 

 habit, and the mammals, except the most primitive, 

 giving birth to active young. Even among the reptiles 

 occasional species are said to 'be viviparous. Such, for 

 instance, are the snakelike lizard or so-called slow- 

 worm (Anguis fragilis) and the viviparous lizard 

 (Lacerta vivipara), both common in England. In these 

 cases, however, the eggs hatch without being laid or at 

 the moment of laying, and there is no arrangement for 

 prolonged nutrition in the body of the parent, as in the 

 higher mammals. It is interesting to note that the 

 marine turtles, now well adapted to sea life, come to 

 land to lay their eggs, thus reversing the procedure of 

 the amphibian. 



2. Reptiles are cold-blooded, with a scaly skin ; they 

 breathe by lungs, which are much less complex than 

 those of mammals and birds. In all living forms the 

 skull has a single occipital condyle; that is, a single 



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