172 Crossing the North and South African Ostrich 



outer enamel layer shows differences in thickness and with it the polished 

 character of the surface. All the eggs are a cream or yellow colour 

 when freshly laid but fade considerably on exposure. 

 Measurements have been taken of 20 eggs as follows : 



TABLE II. 



Measurements of Eggs of South African Ostrich. 

 , Series A Series B 



Thus the average long diameter is 5*92 inches and the short dia- 

 meter 4*92 giving a difference of 1 inch. With such variable structures 

 as eggs a larger series of measurements is desirable in order to secure 

 a more reliable comparison. They serve to show however that on 

 the average the northern egg is about a quarter of an inch longer 

 (6"15 — 5*92 = 0*23 inch) and two-fifths of an inch broader than the 

 southern egg (5"35 - 4*92 = 0'43). The mean difference in the two 

 diameters is 0*8 inch for the northern and 1 inch for the southern, 

 indicating that the former are rounder or less oval than the latter. . 



Eggs from Cross-matings. In breeding for cross-bred chicks the eggs 

 follow the characteristics of the hen whatever the cock may be, that is, 

 the eggs laid by a northern hen mated with a southern cock are large, 

 round and unpitted, while those from a southern hen mated with a 

 northern cock are smaller, oval and pitted. Thus as regards size, shape 

 and surface features, the egg as laid is uninfluenced by the male bird 

 and partakes wholly of the nature of the hen. This is what would 

 ordinarily be expected, seeing that the germ from the cock unites only 

 with the germ of the hen, and scarcely any further change takes place 

 before the egg is laid. As the albumen, shell-membranes and shell are 

 formed in the oviduct of the hen after fertilisation it is difficult to see 

 how the coverings of the egg could be influenced. Instances are adduced 

 however where in crosses of other birds giving differently coloured eggs 



