146 THE INFLUENCE OF INANIMATE SDRHOUXDIXGS. 



fresh water, lives and thrives perfecth' in the Bay of Kiel as 

 well as in the North Sea, and specimens of this fish, caught at 

 Wiirzburg in the month of May, wei'e even placed at once in 

 sea-water without sustaining any injury.^'' 



B. Marine animals in fresh water. — C'ases of this sort are 

 just as frecpient as those we have just been discussing, and 

 occur among both the Vertebrata and Invertebrata. Among 

 the Vertebrata we must first mention the American Manatus, 

 which lives in the great rivers of South America, himdreds of 

 miles from the sea ; then a true dolphin of the genus Glohioce- 

 phalus, which is found far inland in the Irawady ii\er, 600 

 miles from the sea, and which is C|uite different from Glohioce- 





■ r 





Fjg. S7. — Ptalurvsvulcainru<! Twater ^naTcelivmf^in tlie fresh "water lake of Taal (Luzon), 

 and }ta\ mg a paddle like tail. 



phalus indiciis, which lives in the Indian Ocean. Among the 

 reptiles the family of Ilydrophido} contains only sea-snakes, 

 which aie very common in the seas of the eastern hemisphere, 

 and are often found there swimming in the high seas ; it is only 

 at breeding-time that they go to land.*^ The only exception to 

 this rule is found in a new species — here represented foi' the 

 first time — of the genus Plalvrus (fig. 37), which I mvself dis- 

 covered in the fresh-water lake of Taal in Luzon, which is 

 famous for its still active volcano ; it is true that this lake is 

 connected with the sea Ijy a not veiy long river. Together 

 Arith this snake and ass(jciated 'svith typical fresh-water forms — 

 as Nerifiiift, ^felcnda, Falcemon, &c. — other ma\ine animals ai-e 

 found , such as Frishs Perrotteti (the siw-fish), which is very 



