A MoDograpli of the Genus Alaria. 63 



North Sea Water i) respectively, are free from ice. From the data 

 above stated we perceive that the physical conditions of the regions 

 mentioned of the North Atlantic and of the North Pacific are just 

 opposite in relation to the existence and non-existense of Alaria. 

 This apparent contradiction, however, may be easily explained 

 when we consider the origins of the waters of the Baltic Sea 

 and the Japan Sea. 



The Baltic Sea may be compared with, or regarded as, an 

 extensive lake communicating with the Atlantic Ocean through the 

 Skagerak and Kattegat. The Sea is supplied with freshwater from 

 innumerable rivers. The ocean water known as the Jutland Current 

 intrudes into the Sea along the Danish side of the straits. The 

 mass of tlie intruding water is by no moans large enough to have 

 an influence upon the physical characters of the Sea. The water 

 of the Sea is practically supplied by freshwater streams, the greater 

 number ^of which originate in the colder regions. Alaria, which is 

 an open-sea inhabitant, can never intrude into, or exist in, such a 

 freshwater lake. Especially the Swedish side of the strait is wash- 

 ed by this A/ar/rt- lacking water. 



The Japan Sea has two main currents. The more influential 

 one, known as the Tsushima Current, is a branch of the Japan 

 Current and runs into the Sea through the Tsushima Strait, travel- 

 ling towards the north-east along the west coast of Japan. Through 

 the Tsugaru Strait a minor branch goes out into the Pacific Ocean 

 close along the southern shore. The remaining part continues to 

 proceed northward as far as the Soya Strait where it ramifies 

 again into two parts, the major one bending eastwards through 

 the strait and the minor one keeping the original course intruding 

 into the Strait of Tartarv. 



1) Hjobt and Gban: Hydrographie -Biological Investigations. 



