Laws of Fluctuations 733 



for the construction of what is called the line or 

 curve of probability. For this construction the 

 coeflBcients are used as ordinates, the length of 

 which is to be made proportionate to their value. 

 If this is done, and the ordinates are arranged 

 at equal distances, the line which unites their 

 summits is the desired curve. At first glance it 

 exhibits a form quite analogous to that of 

 curves of fluctuating variability, as obtained by 

 the measurements of beans, and in other in- 

 stances. Both lines are symmetrical and slope 

 rapidly down in the region of the average, 

 while with increasing distance they gradually 

 lose their steep inclination, becoming nearly 

 parallel to the base at their termination. 



This similarity between the empirical and the 

 theoretical lines is in itself an empirical fact. 

 The causes of chance are assumed to be innu- 

 merable, and the whole calculation is based on 

 this assumption. The causes of the fluctuations 

 of biological phenomena have not as yet been 

 critically examined to such an extent as to allow 

 of definite conceptions. The term nourishment 

 manifestly includes quite a number of separate 

 factors, as light, space, temperature, moisture, 

 the physical and chemical conditions of the soil 

 and the changes of the weather. Without doubt 

 the single factors are very numerous, but 

 whether they are numerous enough to be treated 



