EFFECTS OF INBREEDING AND CROSSBREEDING. 
It will be seen that the first cross (CO) results in an increase of 12 
or 13 per cent in adult weight, but that at least half of this is lost 
$865,9725 
PLR CENT 
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Fic. 15.—Adult weight, 1917-1920. Comparison between inbred families (2, 13, 32, 35, 39), total inbreds 
(A), random-bred stock (B), first cross (C0), and first generation of renewed inbreeding (C1). Percentage 
differences for males and females averaged. (See Table 9.) 
on renewing inbreeding (Cl). Figure 15 brings out these points 
graphically. 
FREQUENCY OF LITTERS. 
It is conceivable that the heredity of the fetuses might make a 
difference in the number of litters completely absorbed or aborted at 
FO 
Fic. 16.—Regularity in producing litters (litters per mating per year), 1916-1919. Effects of seasonal con- 
ditions eliminated (Table 2). (See Fig. 8 for explanation of symbols.) 
an early stage, and thus make a difference in the frequency of recorded 
litters. As it turns out, however, the frequency of litter (Fig. 16) is 
6448—22—Bull. 1121-4 
