8 



Papers from the Marine Biological Laboratory at Tortugas. 



that the temperature coefficients of all physiological reactions in which 

 metabolism occurs are of the magnitude of the coefficients for chemical 

 reactions, being about 2 or 3. 



The equation for chemical reactions at increasing temperatures may be 

 expressed in the form y = ac", where y is the rate of the reaction at any 

 10° C. temperature interval, a is the rate of reaction at the lowest temper- 

 ature in the series; c is the temperature coefficient, the value of which is 

 usually between 2 and 3; and x is the number of the 10° C. temperature 

 intervals. Thus, if the temperature be raised 10° C, then x = i\\i the 

 temperature be raised 30° C. above the lowest temperature in the series, 

 then X = 2>- Hence, x is the increment of increase in temperature expressed 

 in terms of units of 10° C. 



Harvey (191 1) tested this subject for the rate of nerve-conduction in 

 Cassiopea by experimenting upon two subumbrella rings which were deprived 

 of rhopalia and set into pulsation by means of an entrapped circuit-wave. 

 In being heated from 18° to about 30° C. the rate of pulsation increased in 

 arithmetical proportion to the increment of temperature, in other words, as 

 a rectilinear function of the increase in temperature, not as an exponential 

 function as demanded by Snyder's hypothesis. 



As Harvey was able to obtain only one wholly satisfactory series of 

 observations, it seemed desirable to repeat his experiments. This has been 

 done upon five separate subumbrella rings of Cassiopea, the results being 

 presented in table i , which gives the rates of pulsation of five rings of sub- 

 umbrella tissue of Cassiopea xamachana warmed in sea-water, at Tortugas, 

 Florida. 



Table i. 



> Ring A was first cooled from 27.3° to 17.5°, its rate becoming lower as follows: 27.3° C, 70 per minute; 

 26°, 68 per minute; 24.5°, 72 per minute; 22°, 67.5 per minute; 20.3°, 64 per minute; 17.5°. 54-5 

 per minute. (See Record lA.) 



* This ring was finally heated to 38.75° and then upon being cooled to 28.5° it gave 89 pulsations per min- 



ute, being somewhat weaker than the normal. 

 ' Upon being cooled to 30.5° this ring gave 126 turns per minute. Pulsating normally. 



* Upon being cooled to 26.1° this ring gave 116 per minute. Fully recovered. 

 ' Upon cooling to 29.05° the rate became 120.5°. 



