336 Proceedings of the Royal Society of Edinburgh. [Sess. 
Now when dominance is complete, the dominance ratio from a group of 
factors havingr the same ratio - is 
^ q 
1 + 2 - 
P 
for in the notation of our previous paper 
and 
where a is half the difference between the two homozygous forms 
(3, p. 404). 
The dominance ratio is therefore raised by an excess of factors in 
which the dominant gene is the more numerous, such as occurs under 
genotypic selection. 
8. The Dominance Patio. 
The distribution found for the ratio — or for the value of 0, which 
q 
indicates the same quantity, in sections 3 to 7, enable us to calculate the 
value attained by the dominance ratio under each of the suppositions there 
considered. 
1. In the Hagedoorn condition, where the variance is steadily decaying 
by random survival, in the absence of mutations or selection, 
df = JA sin OdO , 
writing 0 = then p = sin^ q = cos^ 0, * 
whence 
^2 = 8(8'“^) = " sin^ 0 cos^ 0<i0 , 
Jo 
and 
0-2 = S(a2) = 8 Aa2 1 (sm^ 6 cos^ 0 + 2 sin^ cos^ 0)d^0 
Jo 
1 
^ ^ = - 2500 . 
0-2 1 + 2.4 
2. When in the absence of selection, sufficient mutations take place to 
counteract the effect of random survival ^ 
df= 7^ri0, 
IT 
and we have to consider the ratio of the integrals 
rtn- _ riTT 
/ sin^ 0 cos^ 0(70 , / sin2 0 cos^ 0c?0 , 
Jo Jo 
