340 



GEORGE W. BARTELMEZ. 



and the chalazal axis but the axis angle is usually greater than 

 he believed. We cannot be more specific concerning the axis 

 angle in the pigeon than to say that in the great majority of eggs 



50 - 



30 - 



10 - 



20 30* 50 70" 90" 110" 135 



FIG. 2. Curve of variability in axis angles plotted from observations on 506 

 eggs from 90 different birds. The angles could be measured accurately to 5. The 

 eggs were grouped in 10 classes and the number of cases in each class plotted as 

 ordinates, the angles as abscissae. The resemblance to a symmetrical curve of 

 normal variability is apparent. 



the head of the embryo lies in the second octant of the (animal) 

 polar hemisphere. 



THE Axis ANGLES OF INDIVIDUAL BIRDS. 

 My previously published data indicated that the eggs of a 

 given bird show less variation in axis angles than do the eggs of 

 different birds. The following birds were studied for four years, 

 certain of their young mated and their eggs likewise observed. 

 All the birds were the mongrel "homers" of the dealers. The 

 original pairs were given me by Professor Whitman in 1910. 

 They had the freedom of a large attic room where they were 

 free from disturbance, could choose their mates, build their 

 nests and keep comparatively happy throughout the year. At 

 the time I thought there might be some relation between sex 



