536 LIFE AS RELATED TO PHYSICAL CONDITIONS 



The highest perfection of beauty, utility, and productiveness 

 among plants has been reached by those of the land. 



The animals of the land, surrounded by the air, which 

 bears no food solutions to inert mouths, must be well en- 

 dowed with the power of motion in order to procure their 



food. They must either crawl 

 over the surface or be provided 

 with appendages to support their 

 weight against gravity. There is 

 no floating indolently in the air as 

 in the water. Movement, exer- 

 tion, search, are the requisites of 

 life on land. The eggs and young, 

 as a rule, cannot be abandoned to 

 hatch and to care for themselves ; 

 the nest, the burrow, the den must 

 be provided. This is the realm of 

 homes. 



/^ The land animals are also the 



/, lam& I most intelligent. Birds long ago 



solved the problem of flight for a 

 body heavier than air, which is 

 now being successfully solved by 

 man after years of effort. Cer- 

 tain animals, like the bee, the 

 ant, and the squirrel, have the provident habit of storing 

 up food in the summer against a day of need. Other ani- 

 mals, like the birds, have learned to migrate to a warmer 

 clime when winter comes. The beaver is probably the 

 pioneer in hydraulic engineering. When he feels the need 

 of a water reservoir, he builds a dam and makes it. To- 

 day many a swamp in the northern states owes its origin 



BIRD'S NEST 

 A simple home. 



