GEOGRAPHICAL DISTRIBUTION OP ANIMALS 289 



have developed almost independently of one another. To 

 the fresh-water fishes the sea forms equally a barrier, and 



even the shore-fishes very rarely pass across great depths. 

 Eelatively few of the shore-fishes of Cuba, for example, ever 

 cross the deep Florida Straits, and none of those of Cali- 

 20 



