62 LIFE IN THE SEA [OH. 



the oceanic currents afford a powerful means of 

 transport of both animals and plants such as no agency 

 provides on the land. 



So we find that relatively large areas of sea or 

 sea-bottom may possess a fairly uniform fauna or 

 flora the Sargasso Sea in the tropical Atlantic, the 

 intermediate layers of the North Atlantic, or the 

 bottom of the same ocean at over two thousand 

 fathoms depth are examples. Even apart from such 

 cases of wide distribution of a nearly similar life there 

 are cases of the range of isolated species over very 

 large tracts of ocean. Thus some copepods found in 

 the sea off the coast of Ceylon or in the Gulf of Guinea 

 are also found in the waters of the Faroe-Shetland 

 Channel ; and some diatoms inhabiting Chinese seas 

 are now known to occur over many parts of the North 

 Atlantic. Peridinians occurring in the Pacific off the 

 coasts of California are also found off the coasts of 

 Norway. Some species of tapeworms inhabiting the 

 intestines of fishes in the sea off Ceylon also infest 

 British fishes. In these cases the agency of the wide 

 limits of distribution is the oceanic circulation the 

 Chinese and Ceylonese diatoms and copepods have 

 been taken into the Equatorial Stream circulation 

 and so into the Gulf Stream system; the Pacific 

 peridinians have discovered the north-east passage, 

 and have drifted across the North Polar basin ; while 

 the tapeworms probably in their early larval stages 



