460 EFFECT OF TEMPERATURE UPON FACET NUMBER 



strated the fact in the gross anatomy of the echinoderm larvae. 

 Laughlin has recently shown that the various phases of mitosis have 

 markedly different temperature coefficients. Osterhout has pointed 

 out the complications arising from complex systems, in which the 

 various reactions have different Qio values. 



Differentiation and growth are of a necessity synchronized proc- 

 esses. It is at the higher temperatures that the effects of diverse 

 temperature coefficients would be most noticeable. If one stage in 

 development must await another, it is quite obvious that the whole 

 general process would be slackened in speed. At extreme tempera- 

 tures regulation would become impossible. 



As. has been shown, the reaction by which the number of facets is 

 determined is of relatively short duration. It is not complicated 

 by the processes of growth. It shows a true chemical temperature 

 coefficient throughout. 



Metamorphosis involves many long and interdependent processes. 

 The separate reactions do not have the same temperature coeflScients. 

 This is evident from Her twig's curves for a close sequence of stages 

 in the development of the frog tadpole. A rapid reaction must 

 await with its end-products the slower one, before further develop- 

 ment can proceed. The higher the temperature the more erratic 

 will be the separate temperature effects, and the slower becomes the 

 total rate of development. 



It seems reasonable to conclude with Loeb that the straight line 

 feature of physiological reaction curves, together with the special 

 feature of optima, is due to the flattening out of an exponential curve 

 by secondary factors. These factors are not specific such as enzyme 

 destruction, viscosity changes, protein coagulation, or accumulation 

 of waste products, but are the normal results of a differential tem- 

 perature effect on the separate phases of growth, differentiation, and 

 development. 



The Inherited Effects of Temperature. 

 Induction. 



Woltereck working on the size of the head in Daphnia, Middleton on the fission 

 rate in Stylonychia, and Sumner on the length of the feet and tail in mice found 

 that measurable effects could be produced by temperature. Furthermore the 

 effect showed itself in a less degree in subsequent generations, although the 



