330 



VICTOR E. SHELFORD AND EDWIN B. POWERS. 



To determine whether or not this pecuHarity is a reaction to 

 saHnity or alkahnity, the experiment with herring was repeated 

 and carbon dioxide to which the fish are negative (graphs 8 and 

 9) run in the fresh water, to neutraHze the alkahnity. At the 

 beginning of the experiment shown in Chart II., graphs 10 and 

 II, the carbon dioxide content of the fresh water was 26.5 c.c. 



Chart II. 



Graph 8 shows the avoidance of carbon dioxide in sea water introduced at the 

 right. Graph 9 is the control of the same. 



Graphs 10 and 11 show the reaction to fresh water rendered acid by the addition 

 of 26.5 c.c. per liter of carbon dioxide and the reversal of the reaction when the 

 carbon dioxide fell to 8.1 c.c. and finally the gradual reversal to a preference for 

 the fresh water when it became less acid than the salt. 



Graph 12 shows the preference for sea water with oxygen added (right end.) 



Graph 13 shows the selection of essential neutrality by a small salmon. 14 is 

 the control of the same. 



