98 MASS. EXPERIMENT STATION BULLETIN 191. 



that the results of some inbred matings are very good, while others are 

 poor. But, contrariwise, sometimes the results of matings between 

 unrelated birds are poor, while others are good. Nevertheless, matings 

 between urn-elated birds are almost universally approved, while inbreeding 

 is often condemned. 



In this bulletin no attempt will be made to answer most of the questions 

 that arise concerning inbreeding, but evidence that inbreeding may be 

 highly advantageous will be presented. 



The Evidence. 



1. Male No. 8097 produced 10 daughters, by his sister, that averaged 

 155.7 eggs each. The father of this pair also came from a brother-sister 

 mating. On the other hand, male No. 8097 by a half first cousin produced 

 14 pullets that averaged 156.7 eggs each. There is no relation here 

 between the degree of kinship (or inbreeding) and egg production. 



2. The offspring of male No. 8147 by 4 females furnish interesting com- 

 parisons, as shown in the table, and are selected because the whole situation 

 appears here in a nutshell. Eleven daughters bj^ female No. 9420, which 

 laid 221 eggs, averaged 190.1 eggs each. Female No. 9420 is distantly 

 related to male No. 8147 five generations back through a single bird. By 

 female No. 8652, laying 196 eggs, with a much inbred and tangled line of 

 •descent and closelj^ related to himseL^ (see figure), there were 9 daughters, 

 with an average of 181.5 eggs. Moreover, the highest producing individual 

 in the two famihes, viz., B2088, with a record of 237 eggs, was a daughter 

 of female No. 8652. On the other hand, female No. 8418, laying 139 eggs, 

 also closely related to male No. 8147 (see figure), produced 11 pullets sired 

 by him that averaged only 156 eggs each. Finally, there is the mating of 

 female No. 8185 with male No. 8147. This female is related to male No. 

 8147 in exactly the same degree as female No. 9420 (though otherwise un- 

 related to No. 9420) and through the same great, great grandparent. Unfor- 

 tunately her 11 daughters were not all trapnested through the year, as they 

 would have been if there had been any inkling of their importance. We 

 are obliged to fall back on their winter records. Their average for the 

 winter was 42.9 eggs each (which gives an estimated annual average of 

 142.9 eggs), while the daughters of female No. 9420 averaged 75.3 each; 

 those of female No. 8652 averaged 62.4 each, and of female No. 8418, 50.5 

 each. These averages refer to the number of eggs laid before March 1 of 

 the pullet year. Female No. 8185 was a good winter layer herself with a 

 record of 85 eggs and a 365-day record of 185 eggs, but came from a medi- 

 ocre family. 



