MIL] DISCUSSION OF THE DATA OF EYE COLOUR. 151 



respectively. Hence the aggregate of the probable 

 heritages from G : are expressed by the following 

 series : 



D/l x --f 1 x I + - x 2 x ~ + 1 x 4 x I + <fec. ) 



\3 2* 2 4 3 2 9 2 s / 



= DJ^ +(L+_I_+.J__+ & C .}} = D x( + -} = T>xQ-16. 

 (12 \2* 3 x 2 5 3* x 2 6 /) \12 40/ 



So that each grandparent contributes on the average 

 0'16 (more exactly 0*1583) of his peculiarity to the 

 heritage of S, and the four grandparents contribute 

 between them 0'64, leaving 36 indeterminate, which 

 when rateably assigned gives 0'25 to light and 0*11 

 to dark. A hazel-eyed grandparent contributes, accord- 

 ing to the ratio described in the last paragraph, 

 O'lO to light and 0'06 to dark. All this is clearly 

 expressed and employed in the columns II. of Tables 17 

 and 18. 



III. Eye-colours given of the two Parents and four 

 Grand-Parents 



Suppose F to possess D, then F taken alone, and not 

 in connection with what his possession of D might imply 

 concerning the contributions of the previous ancestry, 

 will contribute an average of 0'25 to the heritage of 

 S. Suppose Gr l also to possess D, then his contribution 

 together with what his possession of D may imply 

 concerning the previous ancestry, was calculated in the 

 last paragraph as D x 4 3 o=D x 0'075. For the con- 

 venience of using round numbers I take this as 

 D x 0'08. So the two parents contribute between 



