11 ' ( " : 357 



temperature 1<> SeCUTC B thermal or physiol.i/i< al <.n t.m! an not be 

 i on a mere addition where variable temperature^ arc invoked, for 

 evident lliat every degree baa a <lil' hie in relation ' 



tiiiu- factor. Thus as the mean temperature fuel with tl ice of 



the season both the time for the pupa and the total accumulated 



temperature for the pupa' of the codling moth deCTi li the 



advancing season. Though a fairly constant 'totid elTe< : 

 perature' for any ^iven phase of an life or activity may be 



secured for the summer months when there is a fairly constant | 

 temperature, sueb an accumulation will have no meaning in regard 

 to the same phenomena in spring and fall when the temperatures are 

 more variable. If we wish to be exact, we must secure the temperature 

 curve for the species, based on the observation of a considerable num- 

 ber of individuals kept at different constant temperatures, or possibly 

 better at temperatures having a diurnal variation with constant maxi- 

 mum and minimum, and with fairly constant moisture conditions." 



Krogh on Temperature -velocity. The results obtained by Krogh, 

 which differ in some respects' from those of other investigators, are 

 regarded as highly important. He finds that the temperature-velocity 

 curve expressing the rate at which segmentation takes place in frog's 

 eggs is, between 7 and 20.7, a straight line. "An increase in tem- 

 perature between these limits produces a proportional increase in the 

 velocity with which the processes in the egg leading up to segmentation 

 take place. Below 7 the curve deviates from the straight line and the 

 reaction takes place more rapidly than one would expect from the 

 results obtained at higher temperatures. At the lowest temperature, 

 where the development certainly is no longer normal the curve turns 

 downward once more." 



"The relation between the temperatures and the velocity of embry- 

 onic development is algebraic over a range of temperatures which 

 corresponds approximately to that at which normal development can 

 take place, and the curve representing the relation is consequently a 

 straight line." The velocity of embryonic development is a linear 

 function of the temperature. 



In regard to the relation between temperature and the later stages of 

 development of the frog, Krogh says: "Between the temperatures 1 2 

 and 25 the increment in velocity of the embryonic development of the 

 frog is therefore proportional to the temperature increment, but below 

 12 the development is more rapid than one would expect from the 

 formula." 



