140 STORY OF THE REPTILES 



lizards have the eyelids covered by the outside skin 

 so that they can not be moved. 



In the chameleons the eye-opening may be round 

 and is drawn up Hke an old-fashioned purse — as if a 

 draw-string were around it. One eye can be turned 

 forward while the other is rolled backward, so that 

 the creature can really look two ways at once. This 

 peculiarity is not known anywhere else, though birds 

 and many mammals see two ways at once because 

 one eye is on each side of the head. But both eyes 

 move forward or backward together. ,^ 



We have noted that Tuatera has beneath its srapf 

 the remnants of a third eye, which was once cental 

 in the top of the head. Some other lizards show 

 hints of the same thing; and in the growth of the 

 young of all, there is in the roof of the skull a plaeft^ 

 that is slow to close. This has been supposed by 

 some to be the vestige of the former opening of this 

 third eye. 



The fact that reptiles are so odorous argues that ) 

 they Smell, if there were no other means of inl 

 ring it.' All breathe air through the nostrils wL 

 of course, unlike those of flghes, enter the moj 

 In the crocodilians these enter far back, and 

 soft flap of the palate which drops down in front of 

 them 80 that the creature can keep its mouth open 

 under water and not get strangled ; and at the ex- 

 treme end of the snout, where the nose opens outward, 

 are valves which can be closed to keep the water out. 



In the water-snakes, also, the nostrils open near 

 the tip — really on the upper side of the snout — so 



