4 MASS. EXPERIMENT STATION BULLETIN 443 



The correlation between mothers and daughters in winter clutch size was 

 +.1385. +0135, with linear regression. With 753 degrees of freedom r is statis- 

 tically significant. It is probable, therefore, that the correlation coefficient is 

 significant; but winter clutch size does not furnish an accurate criterion for 

 selecting breeding females to raise the level of intensity, as Jul! (1934) pointed out. 



Dams were classified as phenotypically low in winter intensity if their winter 

 clutch size fell below 3. There were 74 dams in this group with 724 daughters. 

 Very low variability in winter clutch size was anticipated and observed in the 

 dams. Their daughters, however, covered a wide range in clutch size. No sig- 

 nificant correlation between mothers and daughters was observed, although re- 

 gression was linear. 



Medium intensity mothers had a winter clutch size of 3 to 4.5, and 109 indi- 

 viduals fell into this group. The fact should be noted that the mean clutch size 

 of daughters from medium intensity dams was slightly larger than that of daugh- 

 ters from low intensity danis. Again there was no significant correlation between 

 mothers and daughters in winter clutch size, but regression was linear. 



Highly intense mothers had a winter clutch size of 4.6 or more, and there were 

 54 dams in this group with a range in clutch size from 4.6 to 15.5. Daughters 

 from the most highly intense dams exhibited a higher mean clutch size than the 

 daughters ol low or medium dams, but the differences were not great. There is 

 no evidence of a significant correlation between mothers and daughters on the 

 basis of 170 degrees of freedom, though regression was linear. 



These data on Rhode Island Reds indicate some correlation between mothers 

 and daughters in winter intensity for the total population. When the variability 

 in dams was reduced by selecting three possible phenotypes with respect to winter 

 clutch size, this correlation was reduced to insignificance. These facts suggest 

 that winter clutch size depends upon a series of inherited and environmental 

 factors so that a dam's record for intensity is a poor criterion of her transmitting 

 ability. Even dams that were classed as low in intensity failed to breed true, 

 and those grouped as extremely high in intensity failed to transmit this superiority 

 to their daughters with any degree of constancy. 



Correlation in Spring Clutch Size between Mothers and Daughters 



Egg production is generally at a high level in the spring months of March, 

 April, and May. In an earlier report (Hays and Sanborn, 1932), the facts was 

 pointed out that spring clutch size was rather intimately correlated with annual 

 egg production in Rhode Island Reds bred for high fecundity. The value of 

 spring clutch size as a criterion in selecting breeding females requires further 

 study. 



The tabulation of daughters against their mothers gave a coefficient of correla- 

 tion of -f. 1226 + .0139, but regression was not strictly linear. An examination 

 of the regression line shows that digression from linearity occurred in the 113 

 daughters of the 9 dams whose clutch size ranged from 11 to 16. In other words, 

 this small group of extremely intense dams failed to transmit their very high 

 intensity to their daughters. With 733 degrees of freedom, the coefficient of 

 correlation is significant. The above data point to spring clutch size of dams as a 

 poor criterion for selection in breeding for high intensity. 



Mothers have been classed as low in spring intensity if their mean clutch size 

 was below 4.2. The 104 mothers in this class gave daughters whose average 

 clutch size was greater than their own, but the daughters were highly variable. 

 On the basis of 312 degrees of freedom, there was no significant correlation be- 

 tween mothers and daughters. 



