Duerden: Absence of Xenia in Ostrich Eggs 



245 



mated. Knowinj^^ the facts of the case 

 this is certainly what any biologist 

 would expect, though there is no a 

 |)riori reason wh}- the presence of sper- 

 matozoa in the oviduct should not 

 affect the secretion of albumen and shell 

 material; hence it may be that in other 

 lairds some undoubted influence from 

 the cock may yet be established and thus 

 constitute a true case of xenia. 



EGGS FROM CROSS-BRED OSTRICHES 



Naturally the fertilized gemi within 

 the egg from a cross-mating has very 

 different potentialities from the fertilized 

 germ of a mating where both parents 

 are pure, e\'en though the shell is unin- 

 fluenced; and the ostrich derived from 

 the cross-fertilized egg has been found 

 to re^'eal the influence of both parents. 

 The various dimensions and colors of 

 the bod}' and the characters of the plu- 

 mage all show intermediate stages 

 between those of the northern and the 

 southern birds, while a bald head-patch 

 occiuring in the northern and absent 

 from the southern is found to be domi- 

 nant, being present in all the cross-bred 

 chicks. 



The egg laid by a cross-bred hen as 

 regarded its size, form and surface is, as 

 observed above, quite as much a feature 

 of the bird as are the characters just 

 mentioned, and may be expected to 

 follow the one parent or the other of the 

 hen or partake of the nature of both. It 

 is here that the influence of the cross- 



mating reveals itself, not in the egg laid 

 by the i^arent hen with which the cross is 

 made. The average long diameter of 

 34 eggs laid by cross-bred hens is 5.99 

 inches and the a\'erage short d^'ameter 

 5.06 inches, which are practicall\' the 

 same as those of the southern egg (5.96; 

 4.95), but smaller than the northern 

 (6.15; 5.35); the average difference in 

 diameter is 0.93 inch as compared with 

 the 1 inch of the southern and the 0.8 

 inch of the northern egg. Thus the size 

 and shape of the cross-bred egg follow 

 those of the southern bird rather than 

 the northern. The pittings however are 

 intermediate in number and depth. 

 Obvious pittings are found over the shell 

 of eggs from cross-bred hens, compared 

 with their absence in the northern egg; 

 but are neither so plentiful nor so deep 

 as in eggs from southern birds; the 

 general surface is also more i^'or\•-like 

 than in the southern bird but not so 

 unifomi as in the northern. 



The eggs therefore laid by a cross-bred 

 hen reveal undoubted influence from the 

 cross-mating; and the experiments ha\'e 

 further shown that the characters are 

 unaffected according as the cross-bred 

 hens are mated with cross-bred cocks 

 or with a pure northern or a pure south- 

 ern cock. The conclusion reached is 

 that in all cases the egg remains unaf- 

 fected b}' the cock bird, thus demonstrat- 

 ing the absence of xenia as unmistakably 

 as in the first cross-matings. 



