296 



MASS. EXPERIMENT STATION BULLETIN 258 



20 per cent of those used in 1927 lacked pause, and 67 per cent of those usea in 

 1928 lacked pause. The two groups of mothers were alike with respect to 

 winter pause up to 1928. In 1928 check mothers were far superior to inbred 

 mothers in freedom from winter pause. 



The percentage of daughters free from winter pause for the inbreds was as 

 follows: 1926, 22 per cent; 1927, 31 per cent; and 1928, 27 per cent. For the 

 same three-year period, check daughters exhibited 33 per cent, 27 per cent and 

 57 per cent free from pause. These data show that inbreeding has not affected 

 winter pause in the inbred groups, because the inbred daughters of 1928 carried 

 practically the same percentage of non-pause as existed in the inbred daughters 

 of 1923. On the other hand, inbreeding the check birds for three years with 

 selection for absence of pause in female parents has increased the percentage of 

 non-pause birds from 20 per cent in 1923 to 57 per cent in 1928. 



- INBRSD DAMS 



- CHECK DAJIB 



- IKBRID DAUGHTERS 



- CHECK DAUGHTERS 



1927 



1928 



UATINO TEARS 

 CHART 4. — Effect of Inbreeding on Intensity 



Chart 4 points to a very great difference between the percentage of mothers 

 showing genetic high intensity (clutch size 2.6 or more) and the percentage of 

 their daughters showing high intensity. This difference was most pronounced 

 in the inbred group during the first three years. The character of mothers used 

 for inbreeding to produce these daughters should warrant a goodly proportion 

 of high intensity daughters each year. Chart 4 suggests that possibly the 

 inbred mothers laid at a slower rate because of low vigor. This observation is 

 confirmed by the check group, when inbred during the last three years of the 

 experiment. The check mothers used were superior to the inbred mothers in 

 intensity during the first two years reported. 



Inbred daughters were aU decidedly low for intensity even in the first year of 

 inbreeding, in the second year only 30 per cent showed high intensity, and in the 

 third year all lacked high intensity. The check daughters of 1925 had practi- 

 cally the same degree of intensity as in 1923 — about 30 to 33 per cent. 



When the inbred fines were crossed from 1926 to 1928, the resulting daughters 

 showed an inprovement in intensity over previous inbred daughters. The 

 check daughters coming from inbreeding the check lines gave no individuals 

 with high intensity in 1926, 14 per cent high in 1927, and 71 per cent high in 1928. 



These results suggest that inbreeding from a restricted foundation, as used 

 for this inbred group, does greatly reduce intensity. On the other hand, when 



