676 



THE AMERICAN NATURALIST 



[Vol. LI 



TABLE XVIII 



Eelation of Birth Freque; 



The difference between the average progeny from 

 grandparents 1 J* X 1 ? and grandparents 2 X 1 ? is .0579 

 + .02114. This is not three times the probable error, 

 therefore the difference is not significant. The differ- 

 ence between grandparents 1 J' X 1 ? and grandparents 

 1 X 3 ? is .1609 + .08687. This also is less than three 

 times the probable error, hence is insignificant. In fact 

 none of the differences are si^ificant. 



To determine whether birth rank in males or females 

 among the maternal grandparents has effect on transmis- 

 sion, they were compared in the same manner as the sires 

 and dams were. The results for grandsires are : 



The difference between singles and twins is .0534 

 + .0163; between twins and triplets is .1791 + .06559 ; 

 and between singles and triplets is .2125 + .06444. The 

 difference between singles and triplets is 3.62 times the 

 probable error, while the difference between singles and 

 twins is 3.34 times its probable error. 



Treating the dams in the same manner as the sires 

 Table XX is produced : 



