LIFE IN THE PRIMITIVE OCEAN 35 



one which occurred at the period we have reached. 

 There were violent changes of land and water. Great 

 continents, which had for ages spread out very fiat 

 and swampy, were tilted. Mountain-chains arose, 

 with mountain torrents. The rivers, which had been 

 sluggish for ages, became far swifter. This meant a 

 great change for the swimming population. Already 

 the hunt for food and escape was developing swifter 

 means of locomotion. Now the water itself would 

 wash them away if they did not develop more power 

 and speed. No doubt whole vast populations of 

 floating and swimming things perished, and the speed 

 of others was more rapidly developed. 



At the close of these great changes the fish, the 

 king of the early ocean, appears. You see how 

 beautifully his long boat-like body, his powerful fins, 

 his eyes and nose and mouth and teeth at the fore- 

 end, respond to the new conditions. They were the 

 outcome of a very long and hard struggle. And the 

 same geological changes which brought about, or 

 hastened, this struggle and new ''adaptation" are 

 now going to open a new and most important chapter 

 for us. 



