THE SELECTION PROBLEM IN ANIMAL BREEDING 499 
progeny of high performance in the first year she was not retained for 
further breeding purposes. Males for breeding purposes were selected 
on a like rigid basis; they were from high-producing mothers, the daugh- 
ters of which were all high producers, and any male was rejected imme- 
diately if his progeny failed to measure up to high standards. Complete 
individual pedigrees were kept during this period. For the sake of 
comparison low and mediocre strains were also selected on a basis equally 
rigid for their particular characters. 
The success of this type of selection is strikingly evidenced by the 
data set forth in Table LXV, which gives the means from which Fig. 
Taste LXV.—Meran WINTER Eaa Propuction or THE MAINE STATION BARRED 
PuyrmoutH Rock Fiocxs rrom 1899-1915 (Data of Pearl) 
| Nisan winter Number of | Mean winter pro- | Mean winter pro- 
: 2 i . es duction of all duction of all 
eas Peal birds | winter record | WEdS selegted for | birds seleted for 
1899-1900...............| 42.03 | 70 
1900-1901...............| 37.88 85 
1901-1902...............] 45.28 48 
10021003 Gr pee .ae) 26.01 147 
O10 ee] 26.55 254 
1904-1905...............) 85.04 515 
UST ene nea 40.65 635 
HQ0G=1007 -st aane) 22-44 653 
19D7=1908e.. shaman rseses| 119.98 780 
1O08=1909...........-..-| (26.69 359 54.16 22.06 
TOUS SIGN Oe eave ts lace 247 45.57 25.06 
1910-1911...............) 380.49 264 50.58 17.00 
AD Wied Oleh een al eo U8 232 57.42 16.43 
T9IQ=19 13 ee ae 48201) | 182 52.61 
19IS=1014.2.er.2 2.5.5] 52-20 | 192 622000) | 
IQISSIOIDE Ls ew onnce) §40.899 | | 170) | 45.89 | 
Total and means.....| 35.05 | 4,842 | 51.49 | 20.14 
185 was constructed. From an interpretative standpoint, therefore, the 
direct. contrast is brought out sufficiently well in this case, for when 
selection was placed on a fairly rigid genotypic basis it was immediately 
successful. It seems hardly possible to explain the facts of this series of 
investigations by any other than an appeal to the isolation view of 
selection, particularly when consideration is directed toward the rapidity 
with which genotypic selection established high-producing strains in a 
flock which had failed to respond to a rigid system of mass selection. 
Bantam Fowls.—In a previous chapter evidence was presented tending 
toward the general conclusion that the most potent source of that varia- 
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