1886.] 



Family Likeness in Eye-colour. 



413 



That is to say, each parent must in this case be considered as con- 

 tributing 0"30 to the heritage of the child, or the two parents "toge- 

 ther as contributing 0"60, leaving an indeterminate residue of 0'40 due 

 to the influence of ancestry about whom nothing is either known or 

 implied, except that they may be taken as members of the same race 

 as M. 



In applying this problem to eye-colour, we must bear in mind that 

 a given fractional chance that each member of a family will inherit 

 either a light or a dark eye-colour, must be taken to mean that that 

 same fraction of the total number of children in the family will pro- 

 bably possess it. Also, as a consequence of this view of the meaning 

 of a fractional chance, it follows that the residue of 0*40 must be 

 rateably assigned between light and dark eye- colour, in the propor- 

 tion in which those eye-colours are found in the race generally, and 

 this was seen to be (see Table II) as 61*2 : 261 ; so I allot 0*28 out of 

 the above residue of 040 to the heritage of light, and 0*12 to the 

 heritage of dark. When the parent is hazel-eyed I allot f of his total 

 contribution of 0'30, i.e., 0*20 to light, and i, i.e., 0*10 to dark. 

 These chances are entered in the first pair of columns headed I, in 

 Table V. 



Table V. 





Data limited to the eye-colours of the 



Contribution to tbe 

 heritage from each. 



2 parents. 



4 grandparents. 



2 parents and 

 4 grandparents. 



I. 



II. 



ILL 





Light. 



Dark. 



Light. 



Dark. 



Light. 



Dark. 



Light-eyed parent .... 

 Hazel-eyed parent .... 



0-30 

 0-20 



10 

 0-30 







25 

 0-16 



0'09 

 25 



Light-eyed grandparent. 

 Hazel-eyed grandparent 

 Dark-eyed grandparent. 







0-16 



o-io 



0-06 

 16 



08 

 05 



0*03 

 08 



Eesidue, rateably as- 



0-28 



12 



0-25 



t 



0-11 



0-12 



0-06 





