14 AN ANALYSIS OF THE EFFECT OF SELECTION. 
the 1002 inbred plus line; 2 individuals (in cultures 937 and 1074) 
from the Dichet stock; culture 1004, which was made up from exactly 
the same sources as 1002 (see above), and differed from that culture 
only in that a single male was used. 
This material was mated in various ways, but brother-sister matings 
were practised infrequently, and then (see Appendix) not often in 
successive generations. All the cultures in this set were descended 
from the 864 inbred line; and the “generation” of each culture has 
been taken as the greatest number of generations from 864 shown by 
any line of the ancestry of that culture. This method is somewhat 
misleading, since in every case the ‘‘generation”’ thus given is higher 
than the average number of selected generations, and still higher than 
the average number of crossbred selected generations in the pedigree. 
For example, the first culture in the series, 937, is recorded as F3, 
since the father came from the F, generation of the 864 line; but the 
mother was an unselected individual from the Dichet stock. Cul- 
ture 1074 is recorded as F;, though the father was unselected and the 
mother was from the inbred 864 line. Culture 1254 is recorded as 
F,, though one parent belonged to F;, and the only grandparent 
not an F, came from 1074, above. This method of grouping the data 
has been adopted because it is convenient to handle, and because it 
TaBLe 10.—Crossbred Plus Series. 
Generation. n M a T Diff. M. 
Psencas nas 53 | 5.283+0.079 | 0.856+0.056 | ............... —1.217 
) eee eee 417 | 5.211+ .028 -849+ .020] ............... — .719 
ge 's(s gngce ist 812 | 5.489 .018 779% .013 +0.156+0.023 | — .643 
Fee veeseens 1,031 | 5.790+ .012 .599= .008 + .027+ .021 | — .772 
PBosceuecass 1,006 | 5.733 .015 .717+ .011 — .023+ .021 | — .891 
Bigexce scone 877 | 5.616 .018 .790+ .013 — .086+= .023 | —1.423 
save a saoscuae 388 | 5.840+ .024 -711+ .017 — .147+ .034 | -—1.120 
FB jg% anne asens 236 | 5.822 .026 .591+ .018 — .196+ .042 | —1.589 
4,820 
is desirable for purposes of comparison and computation to have the 
generations expressed in whole numbers. The errors involved all 
tend to make it appear that selection has been applied longer than is 
actually the case, and this should be borne in mind when studying 
table 10 and the curve (fig. 5) for this series. The pedigrees may be 
traced from the data in the Appendix, if anyone cares to make a differ- 
ent classification. 
Selection has apparently been successful in raising the mean of this 
series; but this conclusion is not certainly correct, because of the en- 
vironmental possibilities discussed above. 
