452 



POPULAR SCIENCE MONTHLY 



percentages of the average value. This proportional index is called 

 the coefficient of variability. So much then for the principal oper- 

 ations: counting or measuring; seriation of the numbers; determina- 

 tion of the mode, average, standard deviation, and coefficient of varia- 

 bilitv. 



The results of comparative variation studies, so far, fall into two 



3475 [— 



3019 r— 



1947 



ia37 



526 



SO 



_L 



4054 



3631 



3133 



2075 



1485 



680 



.543 

 118 



42 



SOU S2 Si S^ S5 Se 57 SQ S9 60 6l 62 63 64 62 66 67 68 69 10 II 72 7d 74 75 76 77 



Fig. 5. Fkequency Polygox of Statcres of 25,820 American Males ; Lower Polygon, 



OF 100 University Students. 



general categories. First, we have got some notion of the classes of 

 variation polygons that may occur among organisms ; secondly, we have 

 some evidence as to the significance of these different forms. As the 

 science is only about five years old it is l)ut to be expected that a satis- 

 factory solution of even the princijjal j^i'oblems concerning polygon 



