ABSTRACTS. 



301 



this period, as compared with the preceding one, is found in the 

 fact that during this last period all selections for lozv and medi- 

 ocre production have been dropped. The breeding for high 

 production alone continues, with only such differences in the 

 details of manipulation of the breeding stock as would naturally 

 follow a definite knowledge of the mode of inheritance of the 

 character, and of the gametic constitution of particular individ- 

 uals with reference to that character. As a matter of fact, all 

 low-producing lines were dropped at the end of the laying year 

 1911-12. Certain of the mediocre lines were continued a year 

 longer. In the laying flock of 1913-14 there were no birds 

 which had been bred for anything other than high production, 

 so far as the breeder's deliberate intention went. 



The results of this seventeen year selection period are set 

 forth in Table I. 



TABLE I 



Mean Winter Production Per Bird of the Barred Plymouth Rock 

 Flocks from 1899 to 1915 









Mean Winter 



]Mean Winter 





Mean Winter 



No. of Birds 



Production of 



Production of 



Laj'ing Year 



Production of 



Making Winter 



All Birds Se- 



All Birds Se- 





All Birds 



Records 



lected for High 

 Production 



lected loT Low 

 Production 



1899-1900 



41 .03 eggs 



70 







1900-1901 



37.88 " 



85 



- 



- 



1901-1902 



45.23 " 



48 



- 



- 



- 1902-1903 



26.01 " 



147 



_ 



- 



1903-1904 



26.55 " 



254 



_ 



- 



19C4-1905 



35.04 " 



515 



- 



- 



1905-1906 



40.65 " 



635 



_ 



_ 



1906-1907 



22.44 ' 



635 



- 



- 



1907-1908 



19.93 " 



780 



- 



- 



1908-1909 



26.69 " 



359 



54.16 



22.06 



1909-1910 



31.76 " 



247 



47.57 



25.05 



1910-1911 



30.49 " 



264 



50.58 



17.00 



1911-1912 



35.93 " 



232 



.57.42 



16.43 



1912-1913 



43.01 " 



182 



52.61 



- 



1913-1914 



52.20 " 



192 



52.20 



- 



1914-1915 



45.89 " 



179 



45.89 





Totals and means 



35.05 " 



4,842 



51.49 



20.14 



The data of this table are show^n graphically in Fig. 63. 



From the table and diagrams the following results appear : 



I. The number of individuals involved in this experiment, 



on each one of which exact trap-nest records have been kept, 



is large, amounting nearly to five thousand. This number is 



large enough to lead to conclusions which are trustworthy. 



