vin.] 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(3x 1 +1 x24 +3x 2 X2a+9x 4 x2s+d~c.

D112 +(24+3 x 26 +32 x 28 + &c. >}=D x(2+40)-D x0 16.

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, according to the ratio described in the last paragraph, 0.10 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 Gl 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 3-D x 0.075. For the convenience of using round numbers I take this as D x 0.08. So the two parents contribute between