METHODS OF BREEDING 



589 



this second generation should show a very marked improvement in egg 

 production, if breeding be carried on within the line. 



9D168 (S3)X<?D61 



9 E248 (47) X <? 553 

 (Mutant?) 



9F308 (78) 



364 (65) X <? 566 



9 G30 (45) 

 62 (58) 

 "7 (46) 

 197 (88) 

 428 (49) 

 495 (1) 

 Mean of high line, 

 52.8. 



141 (61)X<?DS1 



9 G229 (28) 

 468 (11) 

 Mean of DSl's 

 daughters, 23.75. 



172 (60) Xtf 57 8 -Cross 

 Mean of mutant 

 (high) line, 66.6 



9 E231 (26) X <?552 - 9 F233 (82) X c?573-0 



9 G221 (16) 

 430 (12) 

 ( 477 (1) 

 Mean of main 

 (low) line, 9.67. 



*\*(9fi\V*KK/ I ? F25 (20) 



aid [so] x tfo54 \ YH ,Q^ 



419 (9) X <?551 - 9 F166 (7) X cf 669 

 209 (38) X <?555 - 



363 



- 9F249 (30) 

 Mean of main 

 (low) line, 22.0 



16 (18) 

 163 (19) 

 200 (J*) 

 141 (0) 

 116 (05) 

 161 (11) 

 24 (3) 

 Mean o/ main 

 (low) line, 17.5. 



FIG. 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 

 #248 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- 



