SELIG HECHT 683 



VI. 



In considering the results of this analysis, it is necessary to reiterate 

 a caution previously mentioned. This concerns the amounts of L 

 and of T assumed in the quantitative treatment of the data. The 

 assumption of 1 mol of L at the beginning of the latent period, and 

 of 0.10 mol. of T at the end, in no way affects the analysis except in 

 so far as it makes it possible to present the matter graphically. The 

 actual quantities may be those represented, or, what is more prob- 

 able, they may not. The results of the analysis, however, will be 

 the same, as long as we accept the fundamental idea that a definite 

 amount of the thermolabile substance T must accumulate in the 

 sense organ in order to produce the inner stimulus for retraction of 

 the siphons. 



Considered in such general terms, the relation of the latent period 

 to the temperature may be stated as follows. The duration of the 

 latent period depends fundamentally on the accumulation of a certain 

 amount of material as the result of a single, simple chemical reaction. 

 The variations of this reaction with the temperature are adequately 

 expressed by the Arrhenius equation (3) when ix = 19,680. At 

 temperatures above 21°C., however, this substance which accumu- 

 lates in the sense organ is perceptibly inactivated by heat. The 

 reaction expressing this inactivation is of the kind usually found 

 for spontaneous destructions, and its relation to the temperature is 

 also adequately expressed by the Arrhenius equation when /^ = 

 48,500.. 



We therefore have a destruction reaction, the velocity of which 

 increases more than twice as rapidly with the temperature as does 

 the fundamental reaction which produces the thermolabile substance. 

 At temperatures slightly above 21°, a balance may be struck be- 

 tween destruction and production so that sufficient thermolabile 

 substance will eventually accumulate to produce a response. Soon, 

 however, the destruction reaction is more than fast enough to inacti- 

 vate the thermolabile material as rapidly as it is formed. The re- 

 sult is that no thermolabile substance can accumulate in the sense 

 organ. In Mya this happens at temperatures above 35°C., when 

 no amount of exposure to fight can result in a retraction of its siphons. 



