210 GENERAL BIOLOGY 



plicated and will not be entered upon here. The 

 degree of correlation, i.e. the value of " r," is usually 

 expressed in fractions of unity; in other words, if 

 r = 1.0, then the correlation is complete; if r = 0.0, 

 then there is no correlation. A correlation of 

 .25 or less is usually considered too low to be signifi- 

 cant, whereas one of .75 or more is very high. Fol- 

 lowing are some values of r for various dimensions 

 of man and the flowers of the Celandine (Pearson). 



Stature and upper leg bone .80 to 81 



Stature and upper arm bone .77 to 81 



Stature and fore arm .37 



Stature and cephalic index .08 



Cephalic index and intelligence .029 to .19 



Stamens and pistils (Celandine) .43 to .75 



Stamens and sepals (Celandine) .06 to .02 



Stature, fathers and sons .39 



Brothers (various characters) .49 



There is every reason to believe that similar 

 correlations exist between physiological characters 

 or between a physiological and a morphological 

 character. The inherent difficulties of detecting 

 and measuring physiological characters limit our 

 knowledge in this respect. In the hormones which 

 are manufactured in various organs and transported 

 to other parts to excite physiological response, we 

 can picture a possible mechanical basis for such cor- 

 relations. It is obvious that they may constitute 

 an even more significant factor in the existence of the 

 organism than morphological correlations. An ex- 

 ample of this sort of correlation is afforded by 



