EFFECTS OF INBREEDING AND CROSSBREEDING. 9 
TaBLE 2.—The superiority (+) or inferiority (—) of the record of each experiment to that 
made by the inbred stock at the same time. 
{With respect to the first three characteristics (percentage born alive, percentage raised of those born alive, 
and percentage raised) the difference from the record of the inbred stock is corrected as described in the 
text. With respect to the other characteristics, the differences are given as percentages of the record of 
the inbred stock.] 
| | | 
Percent 
| : uae Birth oe . . iv | Young 
= Percent} raised Birth . |Weight; Size | Litters) Youn : 
cog | born jof those Percent weight, ett. Gain. | we | of | per per pases 
ai gpg alive. | born ‘| total. cd 33 days.) litter. | year. | year Pp 
alive. | ; year. 
| | | 
MMMNSM eS ies tof suniqon| oe) prs sida ce Se 
Saat ae Se eee | ee ee ts 6H ie e236 fea? 9 | eS] ee 
_= 06> oe —1.4} —1.5| —2.8/ 43.4] +6.1] 413.2 | +10.4| +7.8) 1) 27.8 eee 
=», ee ea 42.3} —6.0) —2.3) +2.3| 40.8] 40.3) +0.4| —6.5/} 41.5) —5.1| —7.8 
es. SR +0.7| 44.3) 43.3) +5.8) 44.6] 411.8) 49.0) 44.2] 49.7) +14.3| +161 
= _ pean lied 44.3) —5.3| —0.4) —4.6| —5.2|) —1.1) —2.6! 4+10| —84) —7.5| —1L9 
Other....... 41.0] —16] —1.6/) 42.8) 41.6) 40.6) 41.0) —1.6) —11.9 | —13.3 | —15.2 
| ee 40.5} $11.2) 49.2) 41.7) 42.5] 413.2) 49.0) -1.8) 40.8, —10] 49.5 
i! ar +2.7 | 412.4 | +10.4) 43.6) +3.6|) 411.7) +86) 43.6) +19.4  +23.6|) +47.4 
BG OS 4+7.6| +11.8 | +14.7) +8.8| +81 | 411.9 | +10.5 | +28.3| +9.3 | +40.2| +463.7 
ee +6.9 | +12.0) +14.6 | +12.9 | 49.2 | +21.0 | +16.5 | +14.3 | +36.1 | +55.4 | +82.5 
Se a 49.0} 49.3 +13.9) 410.7) +7.1 | +15.9| +12.5) 410.2 | +33.3 | +46.9| +73.1 
i BS Fiat 43.8} 47.9) +89) 46.7) 44.5) 412.7) 49.8) +4.0 | +25.0 | +29.9| 443.7 
Tieton +9.8| +4.8/ 411.5] +83) 44.5 | 421.7) +15.3 | +14.2 | +17.8 | +34.5 | +56.2 
eee +5.1| +5.9] 48.8) +80] 48.4] 419.5 | +15.3 | +15.1 | +27.0] +46.1| +53.4 
Oe oe +8.6 | +10.8| +14.9 | +10.8) +9.4 | +189) +15.2 | +140) +141 | +30.1| +60.2 
j } j 
The actual differences are shown in Table 30. In Table 2 the 
differences in the case of the weights and fertility are shown as per- 
centages of the record of the total inbred stock. Experiment B, for 
example, produced litters 14 per cent larger than the inbreds. In 
the case of the mortality data, the actual differences shown in Table 
29 are modified to allow for the influence of different basic percentages 
in the inbred stock. To illustrate, 69.4 per cent was the percentage of 
the inbreds raised to 
33 days while Experi- 
ment AC was in pro- 
gress. Only 58.9 per 
cent were being raised 
simultaneously with 
CC. There is more 
room for improvement 
in the latter case. 
Thus the 8.2 per cent 
advance of AC beyond 
the inbreds may mean 
4 
HE FO 11213 BS 72 107. 
————_ 
12/8 /PID 
90,5 45 FD Wi LI 4E 79 2 L3 
JIE 19/7 
Fig. 7—The sex ratio (number of males per 100 females) among the 
young born in the inbred stock during successive 3-month periods, 
1916-1919. 
as much as the ad- 
vance of 11.9 per cent shown by CC. A correction has been applied 
according to the method described in a previous paper (Wright, 1920)* 
in connection with the percentage of white in the coats of guinea pigs. 
Assume that the distribution of the animals in a given stock relative 
to conditions which make for survival or death follows approximately 
a normal probability curve. The area to one side of a certain ordi- 
4 See “Literature cited”’ at end of bulletin. 
6448—22—Bull. 1121—_—-2 
