562 



R. A. SPAETH 



Microscope Stage' Pressure Regulator-'' 



Fig. B Diagram of apparatus for testing the reaction of melanophores to 

 oxygen, to differences of temperature, etc. 



was now closed by a three-hole rubber stopper and a stream of pure 

 oxygen was run into the bottle. The oxygen pressure over the salt- 

 solution 'was kept slightly above one atmosphere by means of a short 

 thistle-tube manometer in which a few cubic centimeters of a 0.1 M NaCl 

 solution served as a valve. The temperature did not vary more than ± 

 0.25°C. during the first forty-five minutes. The melanophores, with a few 

 doubtful exceptions, remained widely expanded throughout this period 

 in all the scales. At the end of forty-five minutes the temperature was 

 gradually raised. The oxygen stream continued to flow. Fifteen min- 

 utes later (one hour after the beginning of the experiment) the tem- 

 perature had risen to 29°C. and all the scales were hght with contracted 

 melanophores. The specimen bottle was now removed to cold water. 

 Two and one-half minutes later the temperature had fallen to 23°C. 

 and expansion was well under way in all the melanophores. One hour 

 and five minutes after beginning the experiment all the scales were 

 again dark. 



The amount of oxygen absorbed by 10 cc. of water in an atmosphere of 

 oxygen at 30°C. (0.26 cc.) is more than four times as great as the amount 

 (0.06 cc.) absorbed at 20°C. by 10 cc. of water exposed to air (Winkler, 

 '89). Although the actual quantity of oxj^gen absorbed by a solution of 

 0.1 M NaCl is less per volume than in water, the same relative condi- 

 tions obtain (Geff cken '04) . In other words at 30°C, in an atmosphere 

 of oxygen a saturated 0.1 M NaCl solution contains more than four times 

 as much oxygen per unit volume as a similar solution exposed to the 



