EDWIN B. POWERS 309 



{e) The Herring (Clupea harengus L.). — The herring (?) used in 

 these experiments averaged from 3 to 4 gm. This fish appeared in 

 great numbers for only a few days. Their sudden disappearance 

 terminated the experiments and prevented the writer from having 

 his identification of the species verified by a specialist. The young 

 of the alewife were running at the same time and were taken by 

 members of the U. S. Bureau of Fisheries. 



The herring (Fig. 2) showed greater differences in ability to ab- 

 sorb oxygen at low oxygen tension with variation in the hydrogen 

 ion concentration of the sea water than any of the other fishes tested. 

 There was a very rapid falling off of the power to absorb oxygen from 

 the sea water when the hydrogen ion concentration was raised at 

 least above a pH of 7.4. It was less rapid when the hydrogen ion 

 concentration was lowered. 



The experiments just described show that the lowest tension at 

 which oxygen can be absorbed from the sea water by certain marine 

 fishes is more or less dependent upon the hydrogen ion concentration 

 of the sea water. Of the five species of fishes tested, the cunner, 

 butter-fish, mackerel, alewife, and herring, the cunner and butter- 

 fish were affected least by a change in the hydrogen ion concentra- 

 tion. The lowest point at which the butter-fish was able to absorb 

 oxygen from the sea water was at 0.35 cc. per liter at a pH of 7.57.^ 

 The mackerel, alewife, and herring were most aflected by the varia- 

 tion in the pH of the sea water; i.e., have the narrowest optimum pH. 

 These fishes are considered the most sensitive and most restricted 

 in their migratory movements. On the other hand, the cunner which 

 is least affected is more cosmopolitan as to habitat and is an all 

 year resident (Sumner, Osburn, and Cole, 1911). The butter-fish 

 which shows less resistance to the variation in the pH is somewhat 

 less cosmopolitan than the cunner in its habitat and is a resident of 

 the Woods Hole vicinity only from early summer to late fall. 



^ This could not be called the optimum pH of the sea water for carrying on the 

 respiratory functions by this fish. At the same time oxygen is being absorbed 

 from the sea water bathing the gills, carbon dioxide is being given ofif. The pH 

 at the beginning of the experiment was 8.28. Thus it stands to reason that the 

 optimum pH of the sea water for this fish would be some where between 8.28 and 

 7.57. 



