50 IN THE GRIP OF AN ICE AGE 



keep a constant high temperature. In cold weather 

 his blood grows colder. Also he lays his eggs — I 

 mean Mrs. Reptile lays her eggs — in the open, and 

 nature must supply the warmth to hatch them. In 

 fine, a coat of scales is not particularly warm. He 

 loves to be in the sun. But we saw that he appeared 

 in an age of perpetual semi-tropical summer, and he 

 prospered and multipHed exceedingly. 



If there had been such things as scientists among 

 those early reptiles, the}^ would have made a strange 

 and disturbing discovery. Let us suppose that they 

 had records of the preceding ten million years. The 

 climate would be recorded as "perpetual summer," 

 as we saw. Surely it would last for ever ! But these 

 reptile scientists would presentl}^ make an unpleasant 

 discovery. The earth was growing colder. If they 

 could have got reports from all parts of the globe, it 

 would have been the same story. Century by century 

 the earth was growing steadily colder. In many 

 places the land was rising, slowly, to unknown 

 heights. Whole regions had to be deserted. The 

 warm-loving vegetation of the tim^e could not live 

 in them. There was no food. The other regions 

 became over-populated. There was the usual fierce 

 struggle and active evolution. The hardier specimens 

 had a better chance. They could live where most of 

 the others could not. Some of them became gradually 

 adapted to a cold climate. 



To drop this little parable, and state the facts in a 



