iv] STATISTICAL STUDY 39 



slope is measured by the size of the angle EOC. The 

 angle made by the diagonal at is 45, the tangent 

 of which is 1 (unity). If there were no correlation 

 the angle would vanish, EF coinciding with CD, and 

 the correlation coefficient would be 0. Intermediates 

 are represented by the value of the tangent of the 

 angle EOC. In practice it rarely happens that the 

 points representing the means of the sons for each 

 class of fathers lie in a perfectly straight line ; when 

 they approach it closely the correlation is called 

 ' linear'; when they depart from it considerably, it 

 is called ' skew/ 



Table of intensity of parental inheritance in different 

 species. (From Pearson.) 



Numbe* 



Mean of Pairs 



Species Character value used 



Man Stature '506 4886 



. Span -459 4873 



"Forearm -418 4866 



Eye Colour '495 4000 



Horse Coat Colour -522 4350 



Basset Hound Coat Colour -524 823 



Greyhound Coat Colour -507 9279 



Aphis Eatio of right Antenna '439 368 

 (Hyalopterus to Frontal Breadth 

 trirhodus) (non-sexual reproduction) 



Water-flea Eatio of Basal Joint of 466 96 

 (Daphnia magna) Antenna to Body length 

 (non-sexual reproduction) 



