DYNAMICS OF MORPHOGENESIS 



179 



TABLE 6 



The relation between the resistances at different temperatures in Series 561, 562 and 

 521 II, reduced to a temperature interval of 10 C. 



in temperature of 10°C. The fact that this coefficient is the 

 reciprocal of the temperature coefficient of chemical reaction, 

 together with the fact that other lines of experiment show that the 

 resistance depends upon the rate of reaction, justify the conclu- 

 sion that this temperature coefficient of resistance is essentially 

 dependent upon the rate of reaction in the planarian body. 



Nevertheless, when substances whose coefficient of distribution 

 increases with rising temperature are used with the direct method, 

 the possibility remains in temperature experiments that the 

 coefficient of distribution may be an important factor in certain 

 •species or certain organs rich in lipoids. It should be possible, 

 however, to show whether it or the rate of reaction in the organ- 

 ism is the important factor in a given case by using some of the 

 depressing agents which show a decrease in the coefficient of 

 distribution between water and fat with rising temperature. If 

 we should find that in spite of the lower coefficient of distribution 

 the resistance of the animals was less at higher than at lower 

 temperatures, or even the same at both temperatures, we 

 should be forced to conclude that the coefficient of distribution 

 was not the essential factor in determining the result. This 

 question will be considered in the following section. 



The results of temperature experiments by the indirect method 

 also afford further evidence bearing upon the point in question. 

 By the indirect method with alcohol as reagent the resistance is 

 less at lower and greater at higher temperatures. It i"s evident 

 that only the differences in the rate of reaction in the organism can 

 be responsible for this result. The animals become acclimated 

 to the reagent less readily and less completely at the lower than 

 at the higher temperature. , 



