AND OF SALINITY. 275 



though decrease of salinity does produce distinct struct- 

 ural changes, yet Schmankewitsch considerably exag- 

 gerated their importance, and deduced from them more 

 than he had any justification for. 



In addition to Artemia, Schmankewitsch * studied 

 the effect of salinity on several other Crustaceans such 

 as Daphnia rectirostris, DapJinia magna, and Branchi- 

 pus ferox. He found that in their case also consider- 

 able structural and physiological changes were brought 

 about, the fresh- and salt-water forms differing, in his 

 opinion, by characters usually held to be specific. 



Equally interesting evidence as to the effect of grad- 

 ual increase of salinity has been obtained by Bateson f 

 in the case of the common cockle, Cardium edule. This 

 mollusc, together with several others, is present in 

 enormous numbers in the brackish waters of the Aral 

 Sea. The waters of this closed basin have been gradu- 

 ally drying up and receding, but the area left exposed 

 " is not a level tract, but contains three considerable 

 depressions, called respectively Shumish Kul, Jaksi 

 Klich, and Jaman Klich. . . These depressions re- 

 mained, for a time, as isolated lakes, each containing a 

 separate sample of the fauna of the sea living in it." 

 As they gradually dried up, becoming salter and salter, 

 the character of the shells progressively changed. To 

 determine this change, samples were collected at vari- 

 ous levels in the lake areas, and were carefully com- 

 pared. On the western shore of Shumish Kul there 

 were seven very definite terraces of muddy salt, show- 

 ing the position of the water at various periods during 

 the gradual drying up. The changes produced con- 



* Ibid. f Phil Trans. 1889, B. p. 297. 



