BROODINESS IN DOMESTIC FOWL. 



Ill 



Constants differing slightly from those given in the table are obtained, 

 if, instead of employing each instance separately in the calculations, the 

 average for each individual bird is emploj'^ed. Whether the instance or 

 the average for each individual bird should be used in calculating the 

 constants depends on which one occupies the center of interest, but 

 whichever method is used, the primary purpose for which this table is 

 presented is not affected. The inconsistencies in the number of individuals 

 occur because it is often possible to determine a character in one individual 

 but not in another. Thus, every bird that becomes broody can be counted, 

 but if a bird becomes broody but once, and does not lay again until the 

 following year, the length of her broody period cannot be measured, and 

 so is omitted in calculating the constants. 



Taking the means (Table VIII) as the basis of comparison, it is clear 

 that the birds of the "non-broody" lines becoming broody in 1917-18 

 had the character much less intensely developed than the broodies of the 

 flocks of 1912-13 and 1913-14 from which they originated. The mean 

 number of times each broody bird became broody is 1.90 against 5.39. 

 Though the average length of each broody period is longer (Table VIII), 

 the total time spent in broodiness by each broody bird is about one-half 

 that of the broodies of the flock of 1913-14. If the entire flocks of each 

 year {i.e., if the non-broody birds are included in calculating the means) 

 are compared with each other the following significant results are ob- 

 tained (Table IX) : — 



Table IX. — A Comparison of the Amount of Broodiness in the Founda- 

 tion Flock, 1912-13, and their Immediate Unselected Descendants, 

 1913-14, f-i-'ith their Descendants selected for the Absence of Broodiness, 

 1917-18. 



Date. 



Number of 

 Birds. 



Mean Number 

 of Days spent 

 in Broodiness. 



Mean Num- 

 ber of Times 

 Broody. 



1912-13, 

 1913-14, 

 1917-18, 



125 

 78 

 106 



65.81 

 68.73 

 10.63 



3.88 



4.91 



.36 



A comparison between the two flocks in respect to egg production 

 (Table VIII) shows that while the 1917-18 flock laid somewhat less rapidlj^ 

 than the 1913-14 flock, the first broody period came later in life (Table 

 X). The mean date of the first broody period is April 18 for the 1913- 

 14 flock, and June 7 for the 1917-18 flock. The 1917-18 flock has a slower 

 rate of production, as shown by the lower percentage production in the 

 initial lajdng period as well as the later laying periods. On the other 

 hand, the length, both of laying periods and broody periods, is longer 



