TEMPERATURE COEFFICIENT OF GROWTH 371 



The temperature coefficient for the development of the tadpole 

 is thus (Qi ) = 1-12. That is to say, if it takes t days at a certain 

 temperature (between 10 and 20), for a certain amount of 

 growth to take place, then it will take t x l-12 n days when the 

 temperature has fallen to - n C. 



(e) Climate. The various meteorological conditions tem- 

 perature, relative humidity, nature of soil, etc., which are all 

 included under the term climate undoubtedly exercise an 

 influence on animal and vegetable growth. The effect of relative 

 humidity on plant growth has been exhaustively studied and 

 conclusions have been drawn as to the concentration of moisture 

 at each temperature which best promotes the growth of specified 

 plants. It is more difficult to get statistics correlating animal 

 growth with the various climatic factors. In order to study 

 biological problems like this experimentally, one must have the 

 power of altering the component factors one at a time and 

 noting the results. 



(/) Seasonal variation. Indubitable evidence is available to 

 show that the growth-rate of the lower animals is subject to 

 seasonal alterations. There are indications that positive and 

 negative variations occur in man in summer and winter respec- 

 tively. 



TABLE LXXIV. 



GROWTH IN HEIGHT OF GERMAN MILITARY CADETS IN HALF 

 YEARLY PERIODS. (DAFFNER.) 



Other investigations (West Point, Sing-Sing, etc.) do not yield 

 such a marked seasonal variation. 



(g) Diurnal variations. Both weight and height vary in the 

 course of 24 hours. The weight is lowest in the morning before 



