86 Pub. Puget Sound Biol. Sta. Vol. 2, No. 37 



sodium carbonate using phenolphthalein as the indicator. The hydrogen 

 sulphide was determined with iodine. 



Reaction to carbon dioxide 



The gas used was supplied by releasing CO^ from the carbonates in 

 the sea water with dilute hydrochloric acid. This was dropped at a 

 calculated rate from a siphon tube and mixed with the right hand inflow 

 current, as described. The temperature was a little above the sea tem- 

 perature. In the graphical records kept, the minutes were represented by 

 vertical distance, and position in the tank by horizontal distance. Each 

 individual was introduced at the center of the tank. 



Some of the results are shown in chart 1. In column 1 the water at 

 the right contained 28 cc. of CO, per liter; that at the left, coming from 

 the water-pipe, contained about 11.2 cc, causing a difference of 16.8 cc. 

 per liter in the length of the tank. The water flow caused the CO, 

 content of the entire tank to be high. The reactions were very marked. 

 All of the blennies soon reached the left inlet and remained with heads 

 pressed against the screen. The tank clearly contained above the opti- 

 mum of COo. 



As a means of comparison a small fish * taken from between 70 

 and 90 fathoms was introduced into the tank, and its very significant 

 movements recorded. After several minutes of rhythmic movement from 

 end to end the departure from the center became less, until after 20 minutes 

 the fish came to rest at the center of the tank. An explanation may be 

 that the deeper sea water, to which the fish was probably accustomed, has 

 a high CO2 content. 



To find the degree of sensitiveness and the optimum CO^ for blennies 

 the COo content was lowered until the ends differed by 7.29 cc. per liter, 

 containing 8.96 cc. and 16.25 cc. per liter respectively. Of 5 individuals 

 used, 1 went to the right as it was introduced and remained ; 2 came to 

 rest near the center with little activity; while the 2 remaining, after some 

 exploration, came to rest at the extreme left. A negative reaction was 

 clearly indicated, although thigmotaxis and faint shadows seemed to play 

 some part. The results suggest that these shore blennies are not only nega- 

 tive to CO2, even in very small quantities, but they are more sensitive 

 than deeper water fish. These results are specially suggestive when con- 

 sidered with the fact that in the water from the habitat of blennies no 

 COo was found as a rule, and the amount was never more than a trace. 



* The specimen has since l)een itlentified as Oligocottiis maculosus and proliaMy entered the 

 dredge much nearer the surface than was at first supposed. However, having a different environ- 

 ment from the distinctly sliore species, its reactions are of value in comparison. 



