34 T^HE COMING OF MAN 



phibia are born in the water, those of all higher animals on 

 land. The eggs of the amphibian are far larger and less 

 numerous than those of the average fish; but far smaller than 

 those of reptiles. The decrease in the number of eggs is 

 alarming. Fish produce eggs by thousands or even millions, 

 amphibia by hundreds, reptiles perhaps by tens, birds and 

 mammals by still smaller units. 



This condition can be remedied and its dangers averted 

 only by a steadily increasing and best possible care of the 

 young. We find little of this in most reptiles, much in birds; 

 in all higher mammals the eggs are carried in the body of the 

 mother until birth, and the care of the young is continued 

 for a steadily increasing infantile period after birth, which 

 in higher mammals and man is followed by a period of child- 

 hood. Em.ergence on land revolutionized vertebrate life; evo- 

 lution in the face of limitations and opposition often becomes 

 revolution. The ice formed during a long hard winter blocks 

 the channel and holds back the gathering flood. Either the 

 ice gives way or the water seeks and ploughs out a new channel 

 to its goal. 



We have left our amphibians far behind and must return 

 to them and their descendants. The mud-puppy of our lakes 

 gives us a good example of a primitive amphibian; the newt or 

 salamander of a far more advanced form. Frogs and toads 

 represent a late, greatly modified and very peculiar 

 branch. 



From some primitive amphibian the reptiles diverged in 

 all directions. The primitive reptiles were creeping forms, 

 sometimes dragging the body on the ground. But the legs soon 

 strengthen and lengthen as in lizards. The reptiles soon out- 

 grew the difficulties of land life, found abundant food and 

 easy place. They were very precocious and advanced rapidly. 

 During Mesozoic time there were running, striding and even 

 flying forms. The huge, well-armed dinosaurs ruled the 

 world, and it seemed as if no other form could ever compete 

 with them. It was a marvellous class of vertebrates with a 

 fascinating history into- which we have no time to enter. 



