METHODS OF BREEDING 589 
this second generation should show a very marked improvement in egg 
production, if breeding be carried on within the line. 
9 F308 (78) 0454 —0 
2 G30 (45) 
62 (58) 
117 (46) 
197 (66) 
428 (49) 
495 (1) 
Mean of high line, 
Q E248 (47) X 7553 52.8. 
(Mutant?) 
9 G204 (41) 
166 (49) X 7 D31 264 (15) 
2 G229 (28) 
141 (51) X @D31 { 458 (11) 
Mean of D31’s 
daughters, 23.76. 
172 (60) X #878 — Cross 
Mean of mutant 
(high) line, 66.6 
9 D168 (33) X 7 DE1 
Q E231 (25) X (562 — 9 F233 (32) X S573 —0 
@ G221 (16) 
419 (9)K *651— QF165 (7) X S569 430 (12) 
477 (1) 
209 (38) X #555 — 0 Mean of main 
(low) line, 9.67. 
313 (26) X F554 ee - 
363 (11) X 7560 — 9 F249 (30) 
Mean of main 
15 (18) (low) line, 22.0 
163 (19) 
200 (12) 
141 (0) 
116 (28) 
151 (11) 
24 (23) 
Mean of main 
(low) line, 17.6. 
Fic. 227.—Pedigree of line D61D168, characterized by low winter egg production. 
Conventions are the same as in Fig. 226. The progeny of the mutant (?) high producer 
E248 is included in this pedigree. (After Pearl.) 
This method of increasing egg production is not entirely theoretical, 
but it has actually worked after 9 years of patient selection of high 
trap-nest performers failed to show any improvement. The two pedi- 
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