184 



BIOLOGY ОГ THE SF.AS OF THE U.S.S.R. 



Fig. 78. Chart of circulation of surface waters of the 

 White Sea (Timonov). 



The Dvina and Kandalaksha Gulfs are in free communication with the 

 central parts of the Sea, but the shallow Gulf of Onega is barred from the rest 

 of the Sea by the Solovetsky Islands. In consequence of its shallowness and of 

 the strong tidal streams the waters of the Gulf of Onega are generally well 

 mixed from top to bottom, and are homothermic and homohaline. The Gulf 

 of Onega is the part of the Sea which is best warmed in summer and best 

 aerated, by virtue of which animal forms find here for themselves the most 

 favourable conditions of existence. 



Fig. 79. Distribution of the Crustacea 

 Calanus finmarchicus (7), plankton ciliates 

 Cyttarocyllis denticulata (2) and Tintin- 

 nopsis campanula (3) in the White Sea (Der- 

 jugin from Virketis, 1928). 



