474 



GROWTH 



X 



10 



= 3-25, 



I.e. 



Therefore 

 and 



10 log X = log 3-25 =- 0-5119. 

 \ogx = 005119, 

 X =- 1-125. 



The temperature coefficient for the development of the tadpole 

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

 temperature 9° (between 10° and 20°), for a certain amount of 

 growth to take place, then it will take t X 1-12" days when the 

 temperature has fallen to ^ — n° C. 



{e) Climate. The various meteorological conditions — tempera- 

 ture, 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 LXXXV.). 



TABLE LXXXV 



Growth in Height of German Military Cadets in Half- 



Yearly Periods (Dafpner) 



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

 such a marked seasonal variation. 



