264 SOME RESULTS OF OSTRICH INVESTIGATIONS. 



northern egg is about a quarter of an inch longer (6.15 — 5.92 

 = 0.23 inches) and two-tifths of an inch broader than the 

 southern egg (5.35 — 4-92 = 0.43). The mean difiference in 

 the two diameters is 0.8 inch for the northern and i 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 charcteristics 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 vmpitted, 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 

 (^gg, as laid, is uninfluenced l)y 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 tliC hen after fertilisation, it is 

 difficult to see how these coverings of the egg could be influenced. 

 Instances are adduced, however, where in crosses of other birds, 

 giving differently-coloured eggs, the cock seems to exercise some 

 influence, the i)henomenon being known as Xenia.''' The diverse 

 character of the eggs of the northern and southern ostrich afford 

 a good test of the possibility of Xenia occurring in birds, but 

 from none of the cross-matings has any support for the pheno- 

 menon been forthcoming. 



Eggs from Cross-bred Hens. — In cross-bred hens are natur- 

 ally combined the possibilities of both the northern and the 

 southern parents, and the characters of the eggs laid by them are 

 just as much a part of the make-up of the bird as are the more 

 obvious body features. The question therefore arises whether 

 the eggs laid by cross-bred hens will follow those of one parent or 

 the other, or be something intermediate between the two. Scores 

 of eggs laid by cross-bred hens have been examined at the nest 

 and in the incubator, and in all cases have been found to be 

 intermediates as regards size, shape, and the nature of the 

 shell between typical northern and southern eggs. Obvious 

 ])ittings occur over tlie shell, often more numerous towards the 

 air-chamber end, but are never so plentiful nor so deep as in the 

 eggs from the southern bird. The egg has neither the full size 

 nor the roundness of the northern ostrich, but is larger than the 

 southern, and its general surface is more enamel-like. Naturally 

 variations occur in the eggs laid by dififerent hens, and sometimes 

 they approach those of the one parent more nearly and sometimes 

 those of the other. The degree of pitting and smoothness of the 

 surface of the shell do not admit of more than a general statement, 

 l)Ut the dimensions of 34 cross-bred eggs are available for com- 

 l^arison wjth those of the northern and southern eggs. 



*Jourii. of Hcrrditv, 6 



