192 The Under-Water World 



was accounted for in all kinds of fantastic 

 ways. Many were supposed to have had 

 their origin in slime and mud. The ob- 

 servations of fish migrations were also 

 exploited profitably by the augurs of all 

 countries. 



Fishes abound principally in shallow 

 waters, or those of middle depth. From 

 a depth of 400 fathoms downwards, fish 

 life becomes increasingly scarce. On the 

 other hand, from 400 fathoms and up- 

 wards, it is within easy reach of the 

 shore, and subject to the continual 

 fluctuations of the tide, which may rise 

 and fall but a few feet as in the Mediter- 

 ranean, or retreat for several miles as off 

 the coast of Brittany. 



The appearance or otherwise of fishes 

 depends primarily upon the disposition 

 of the egg. Fish eggs may be roughly 

 divided into two classes, the free swim- 

 ming and the anchored. Sea water tends 

 to be more saline in mid-ocean than close 



