46 SAVAGE SUKVIVALS 



species there still exist remnants of these lost 

 toes. 



The *^ glass-snake '' looks very much like a 

 cousin of the common garter snake. But it is not 

 a snake at all. It is a lizard. And it is so classed 

 in all the books. 



Snakes are limbless lizards. When we find a 

 lizard without legs, we call it a snake. And when 

 we find a snake with legs, we call it a lizard. The 

 ** glass-snake'' is a lizard because it has four legs. 

 But its legs are not visible. They are internal. 

 The ** glass-snake'' is a lizard on the way to be- 

 coming a snake. We catch it in the act. It is a 

 connecting link between these two orders of rep- 

 tiles. The legs have gone out of use, but not long 

 enough ago for them to have passed out of exist- 

 ence. They are vestigial. In the bodies of some 

 snakes, as the pythons and constrictors, there are 

 little clawed remnants of hind limbs. 



Snakes have only one lung. They have come 

 from ancestors with two lungs, but their body is 

 so narrow that there is not room for two lungs 

 side by side, so one lung has been abandoned, and 

 the other one has become larger by extending out 

 along the body. The abandoned lung still exists, 

 but it is a mere unused remnant. 



The right ovary of birds has become atrophied 

 in a similar way, all of the eggs of birds being pro- 

 duced by the left ovary. The ovary is the egg- 

 producing organ of animals. In nearly all animals 

 there are two ovaries, just as there are two kid- 



