142 THE HAUNTS OF LIFE 



its ancestors were deep-water fishes. Similarly, 

 though the flounder is often found in rivers 

 20 miles from the sea, it does not spawn in 

 fresh water, it must go back to its old home in 

 the shallow sea. It will be interesting to think 

 out some cases that seem to break this rule. 



It is also to be remembered that some animals 

 are at present making the transition from salt 

 water to fresh. The flounder is a case in point, 

 undoubtedly a marine fish, but becoming more 

 and more accustomed to the rivers. The 

 quaint Manatee, included with the Dugong in 

 the small order of mammals, known as sea-cows, 

 or Sirenia, is typically a coastal mammal, but it 

 goes far up the rivers, and it is now found, for 

 instance, in the Everglades of Florida, a far cry 

 from the sea. 



In any case we should not think of the fresh- 

 water fauna as a fixed and finished assemblage 

 of animals. It is a noteworthy fact that many 

 fresh-water animals spend only a part of their 

 lives in the fresh water. Some of these seem 

 to be still in process of accustoming themselves 

 to it, others to be leaving it for salt water, and 

 others again are apparently on the way to 

 becoming land animals. 



How can we tell in which direction a par- 



