CHAPTER XXXVI 



IN THE LITTLE BROOK 



ONG ago, in the old Devonian times, when life 

 was very leisurely, all the beasts and people that 

 there were lived in the sea together. The air 

 was dull and murky on the land. It was so Hght 

 that it gave no support to the body, and so those that ven- 

 tured about in it had to lie prone on the ground all the time 

 wherever they went. So they preferred to stay in the water, 

 where motion is much easier. Then, too, water is so much 

 better to breathe than air, if one has gills fitted for it. He 

 has only to open his mouth and the water rushes in. Then 

 he has only to shut his mouth and the water rushes out 

 backward, bathing his gills on the way. Thus, the air dis- 

 solved in the water purifies all the little drops of blood that 

 run up and back through the slender tubes of which the gills 

 are made. 



But in those days, besides the gills, some of the fishes of 

 the sea had also a sac in the throat above the stomach in 

 which they could stow away air which they took from the 

 atmosphere itself. This served them in good stead when 

 they were in crowded places, in which the air dissolved in the 

 water would fail them. 



And those which were so provided used to venture farther 

 and farther out of the water, pushing their way heavily on 

 the ground. And those which could put forth most effort 

 survived, until at last their descendants were able to main- 

 tain themselves on the land together. These gave rise to 

 the races of reptiles and birds and mammals, the ancestors 

 of all the land beasts that you know, as well as men and 



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