APPLICABILITY OF A COEFFICIENT OF CORRELATION 351 



upon such biological theories as DRIESCH S annunciation that in a dif 

 ferentiated system the proportionality of the parts is absolutely inde 

 pendent of the size of the system. 



In dealing with materials of economic importance, the method has 

 been applied to the problem of the relative proportion of sterile spike- 

 lets in varieties of wheat with varying numbers of total spikelets per 

 head, to the relationship between total solids and sucrose content in the 

 juice of sugar beets, and has been found of the greatest value in analyz 

 ing the relationship between the egg production of the individual months 

 and that of the entire year in the domestic fowl. 



These illustrations are perhaps sufficient to show that the coefficient 

 has great analytical value, and should have the widest usefulness. 



Finally it must be understood that the conclusions drawn from the 

 illustrations given in this paper are not in all cases to be extended be 

 yond the specific series of data to which the formulae have been applied. 

 The data employed are, in some instances, intended to illustrate the type 

 of biological problem to which the formulae may be applied when more 

 extensive data are available. No attempt has been made to discuss in 

 detail the biological significance of results of so diverse kinds of illus 

 trations. Such discussion must be left to the specialist in the particular 

 field in which the observations fall. 



LITERATURE CITED 

 DARBISHIRE, A. D., 1904 On the result of crossing Japanese waltzing with albino 



mice. Biometrika 3 : 1-51. 

 GRANTHAM, A. E., and GROFF, F., 1916 Occurrence of sterile spikelets in wheat. 



Jour. Agr. Res. 6: 235-250. 

 HARRIS, J. ARTHUR, 1909 a The correlation between a variable and the deviation of a 



dependent variable from its probable value. Biometrika 6 : 436-443. 



1909 b Correlation in the inflorescence of Celastrus scandcns. Ann. Rep. Mo. 

 Bot. Card. 20: 116-122. 



1910 a A quantitative study of the morphology of the blood root, Sanguinana 

 canadense. Biometrika 7 : 305-351. 



1910 b The arithmetic of the product moment method of calculating the co 

 efficient of correlation. Amer. Nat. 44 : 693-699. 



1912 Biometric data on the inflorescence and fruit of Crinum longifolium. 

 Ann. Rep. Mo. Bot. Card. 23: 75-99. 



1913 On the relationship between the number of ovules formed and the capacity 

 of the ovary for maturing its ovules into seeds. Bull. Torr. Bot. Club 40 : 



447-455- 



1914 a On the relationship between the number of ovules formed and the number 

 of seeds developing in Cercis. Bull. Torr. Bot. Club. 41 : 243-256. 



1914 b Further observations on the relationship between the number of ovules 

 formed and the number of seeds developing in Cercis. Bull. Torr. Bot. 

 Club 41 : 533-549- 



GENETICS 3: Jl 1918 



