Laivs of Fluctuations 733 



for the construction of what is called the line or 

 curve of probability. For this construction the 

 coefficients 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 the curves 

 of fluctuating variability, obtained by the meas- 

 urements of beans and in other instances. Both 

 lines are symmetrical and slope rapidly down in 

 the region of the average, while with increasing 

 distance they gradually lose their steep incli- 

 nation, becoming nearly parallel to the base at 

 their termination. 



This similarity between such empirical and 

 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 thev are numerous enough to be treated 



