1 86 EXPERIMENTAL EVOLUTION LECT. 



interesting fact that some of the animals accustomed 

 to salt water did very well when suddenly transferred 

 into fresh water, and also when, a month later, they 

 were again suddenly replaced in the salt solution, 

 although, in the latter case, animals of the same 

 species die immediately when they are placed in salt 

 water without having been gradually accustomed to it 

 by small doses of salt. 



In another series of experiments Beudant tried to 

 accustom marine animals to fresh water. These 

 animals, of the genera Haliotis, Cerithium, Buccinum, 

 Tellina, Verms, Ostrea, Pecten, Mytilus, when suddenly 

 immersed in fresh water soon died, although some of 

 the littoral species certainly seemed to resist longer. 

 After this experiment Beudant tried to accustom the 

 same species gradually. He had thirty-eight species 

 at his disposal, in great numbers, and performed the 

 experiment as in the converse case, adding fresh water 

 every day, so that after five months the animals were 

 living in pure fresh water. Out of thirty-eight species, 

 twenty withstood the change perfectly well ; 370 out of 

 610 being alive in fresh water, while in salt water 

 there were 401 ; while the eighteen others were unable 

 to exist. 



Lastly, in a third series of investigations, Beudant 

 established the fact that marine molluscs are able to 

 live in sea water containing 30 / of common salt, a 



