244 



The Journal of Heredity 



otlurwisc el \cnia. The c<,'k t'f ^^e 

 northern bird is ahva>'s larger than that 

 of the southern . the shell is almost free 

 from obvious ])ores or pittin^s, and 

 presents an i\-ory-likc, smooth surface. 

 Usuall>- also the northern e^j;,'^ is rounder 

 in shajje or less o\a\, the two diameters 

 beinj,' more nearly equal. On the other 

 hand the e^fj of the southern bird is 

 distinctly oval and is deeply pitted all 

 over the surface, the pits often larger 

 and more ])lentiful around the air- 

 chrunber end; and in consequence of the 

 pittin).,'s the surface does not ]:)rcsent the 

 ivor\- smoothness of the northern e^j.^. 

 Both however are of the same cream 

 color when freshh' laid, becoming lighter 

 on exjjosure. Among a number of eggs 

 from northern and southern birds mixed 

 together no mistake could possibly be 

 made in separating the one kind from 

 ihe other. 



As regards actual dimensions the 

 average long diameter of 43 northern 

 eggs was 6.15 inches and the short 

 diameter 5.35 inches; the average long 

 diameter of 22 southern eggs was 5.96 

 inches and the short diameter 4.95 

 inches. Thus on the average the north- 

 em egg is about one-fifth of an inch 

 longer and two-fifths of an inch broader 

 than the southern egg; the former has 

 an average weight of 3 j^ounds 1 1 ounces 

 and the latter of 3 pounds 3 ounces. 

 The mean diflference in the two dia- 

 meters 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. 



The jjitting which gi\'es such a 

 charac-teristic difference to the ap- 

 ]X'arance of the two Icinds of eggs is 

 associated with the resjnratory ])ores 

 of the shell. In the northern egg pores 

 occur, but are so small and ojxn so 

 close to the surface as to be scarcely 

 visible to the naked eye, and are mostly 

 scattered .singl>- with but little groui)ing. 

 In consecjuence the surface ai)i)ears 

 almost uniform!}' smooth, though a line 

 ])itting can ])e detected with a lens. In 

 the s<juthern egg the res])irator\' ])ores 

 are larger, sunken below the general 

 surface and mostly in small groups, 

 varying from about six to twelve in a 



groujj. The close grouping of the 

 sunken jjores gives rise to the deeph- 

 pitted surface of the shell, often cmplia- 

 sized in the nest b\- the adherence of 

 small particles of earth. 



Whether the northern and the south- 

 eni ostrich are to be regarded as distinct 

 species dejjends largely ui)on one's 

 conception of the term species. At any 

 rate the two are found to interbreed 

 freely and reciprocally, and the crosses 

 or hybrids ha\'e also been ]3rovcd to 

 breed freelw both inter se and with 

 either of the jjarent fonns. About 200 

 eggs from the cross-matings ha\-e hither- 

 to been obtained, both from Nigerian 

 cocks mated with Cape hens and from 

 Cape cocks mated with Nigerian hens. 

 Breeding ostriches are kept aj^art from 

 all others in large fenced camps, a 

 breeding set consisting of a single cock 

 and one or two hens; and there is never 

 any ])ossibility of confusion as to the 

 ])airings and the indix'idual hen laying 

 the twelve to eighteen eggs which con- 

 stitute a nest. 



The nests are visited from time to 

 time to observe their progress, and in 

 view of the possibility of xenia occurring 

 the characters of all the eggs have been 

 closely noted. Without any hesitancy 

 it can be stated that in no case have the 

 eggs sho-dfi any injiiicncc frani the cock'; 

 northern liens mated iinth southern cocks 

 have alu'ays laid large, rounded, smooth, 

 unfitted eggs and southern hens mated until 

 northern cocks have always laid smaller, 

 more oval, deeply pitted eggs. The 

 experienced eye can at a glance dis- 

 tinguish one kind of egg from the other 

 as regards size, shape, nature of the sur- 

 face and i)itting; and in no instance have 

 the eggs been difTerent from those which 

 one would expect from the hen in-espec- 

 tive of her mating, or e\'en when un- 

 mated. 



It can therefore be regarded as estab- 

 lished that so far as concerns the egg of 

 the ostrich there is no e\idence whatever 

 of the jjhenomenon of xenia. The size 

 of the oN'um, amount of albiunen and 

 nature of the shell are the characteristics 

 of the hen just as much as are the 

 external bodily features, and are unin- 

 fluenced b\- the cock with which she is 



