APRIL 61 



"continental shelf." As we pass out into 

 the Atlantic from the eastern shore of the 

 United States, the water grows deeper only 

 very gradually until we have gone out about 

 one hundred miles. Here it drops very 

 abruptly into depths far greater than any 

 known nearer the land. This is the true 

 edge of the American continent; and just 

 beyond is quite possibly the home of the 

 shad. 



The pressure of the water at great depths 

 is so heavy that few fishes are adapted for 

 life there and at the surface too. But the 

 shad has a strange series of tubes in his 

 head to which water may be admitted, and 

 these probably are a part of the mechanism 

 that helps him to adapt himself to these 

 varying conditions. 



THE RUN UPSTREAM 



As spring comes and the water grows 

 warmer the shad rise to the surface and 

 make their way to the nearest river. It was 

 for a while thought that each shad returned 

 necessarily to the river in which he was 



