240 
GENETICS: HARRIS, BLAKESLEE AND WARNER 
tation is that the egg yolk in its growth abstracts fat-soluble pigment 
from the food, thus precluding its localization in the body tissues, or 
that it actually withdraws the pigment from the tissues. 
This view is supported by a number of hues of evidence. First, the 
correlation between October pigmentation and the egg production of 
the preceding months decreases (but, as is shown in Figure 2, not 
regularly) as the time at which egg production is measured becomes 
more distant from that at which the measurement of pigmentation was 
taken. 
Again, in comparing pigmentation as measured in October of the 
second year with egg production in November of the pullet year, it is 
found that pigmentation decreases but slightly and irregularly, though 
apparently in a linear manner, with increasing egg production. In 
comparing October pigmentation with Octo- 
ber egg production of the same (second) year, 
one notes that pigmentation decreases very 
rapidly as one passes from birds which have 
laid no eggs to those which have laid 1, 2, 3 
or more eggs, but that this decrease soon falls 
off so that birds which have laid over 6 or 7 
eggs are apparently sensibly alike in the 
amount of yellow which they exhibit.^ 
The same point may be brought out if a 
series of measurements be arranged to show 
the percentage of birds of various pigmenta- 
tion classes which are laying* or 'not lay- 
ing' at the time the color determinations were 
made.^ As shown in Figure 3 the percentage 
of the birds which are laying falls precipitously from 87.8% among those 
showing only 6 to 10% yellow (centered at 8% yellow) to practically 
zero for all grades of yellow above 30%. The average number of days 
since laying represented by the heavy line in Figure 3, is also a val- 
uable indication of the direct relationship between egg production and 
pigmentation. Beginning with an average of only 0.4 day since lay- 
ing in the 6 to 10% color class, the average length of time since laying 
increases rapidly from birds with smaller to those with larger amounts 
of yellow pigment. 
Finally, the problem may be approached statistically as follows: 
If the relationship between percentage of yellow and egg production 
be chiefly of a physiological nature, it is quite conceivable that the 
correlations between the October percentage of yellow and egg produc- 
