238 
GENETICS: HARRIS, BLAKESLEE AND WARNER 
For 1913-1914, E = 204.754 - 1.459 y, 
For 1914-1915, E = 212.058 - 1.416 y, 
where E = total eggs laid per year and y = per cent yellow in ear 
lobes. Since yellow has been recorded in units of 5% range, the actual 
difference in egg production associated with a difference of one work- 
ing unit in pigmentation is about seven eggs. 
PER CENT. YELLOW 
/S 25 3S 4S SS 6S IS 
FIG. 1. 
The practical significance of the differences in egg production indi- 
cated by this equation may be most readily seen from a little table 
showing the actual mean annual egg production of the birds grouped in 
classes of 15% range in ear lobe pigmentation. 
PER CENT YELLOW 
1913 
-1914 
1914 
-1915 
IN EAR LCBES 
Number of birds 
Mean number of 
eggs 
Number of birds 
Mean number of 
eggs 
10-20 
25-35 
40-50 
55-65 
70-80 
83 
67 
111 
46 
2 
187.0 
148.2 
136.7 
132.1 
76.5 
81 
72 
119 
90 
13 
185.1 
172.2 
148.4 
126.9 
111.5 
It is clear that by selecting, in October, birds with 10 to 20% yellow 
it is possible to obtain a group which have averaged over 30 eggs more 
than the flock as a whole and over 50 eggs above the average of the 
class with 55 to 65% yellow. These differences are not merely very 
