THE CONQUEST OF THE DRY LAND 209 



Except in the case of some sprawling 

 creatures, like centipedes and snakes, the body 

 of a land animal tends to be compact. The 

 weight has usually to be lifted and supported 

 off the ground, whereas in an aquatic animal 

 the weight is supported in the water. An 

 animal like a jelly-fish is unthinkable on land. 



NEW WAYS OF LOOKING AFTER THE 

 YOUNG 



The conquest of the land necessarily means 

 new ways of looking after the eggs or the 

 offspring. For the aquatic animal, it is often 

 enough simply to liberate the eggs into the 

 water, which serves as their soft cradle ; but it 

 would be fatal in most cases if a land animal 

 merely laid its eggs or its young ones on the 

 ground. They would be dried up or devoured. 

 So we find many ways in which safety is 

 secured, e.g. by burying the eggs in under- 

 ground nests ; or by keeping the young ones 

 within the mother's body for a long time before 

 birth, so that they are not very helpless when 

 born ; or by carrying them about after birth, as 

 in kangaroos and opossums. 



One of the ways of securing the safety of 

 14 



