J. K. DrKHDKN 171 



TABLE I — rontitiMt/. 

 HcriM C S4TioH 1) 



Average fil9 5 37 



Averat^e ri-14 5-34 



Thus the jivmigo long diameter of 4M northern eggs is (Mo inches 

 and the short diameter 5'35 inches, representing an average difference 

 between the two axes of ()"8 inch. 



Egg of South African Ostrich. The egg of the southern bird is 

 deeply pitted all over the surface, and pits often larger and more plentiful 

 at the air-chamber end, hence the shell does not present the ivory 

 smoothness of the northern egg. A Cape hen will sometimes prcnluce 

 a neiirly smooth, round vgg, but never to so marked a degree ;is th«' 

 typical Nigerian hen. Also the latter may occasionally lay eggs with 

 deeper pittings than usual, especially in the first one of the season. 

 Among a number of eggs from northern and southern birds mixed to- 

 gether no mistake can however be made in separating the one type from 

 the other. 



The pitting which gives such a marked character to the southern egg 

 is jissociated with the respiratory pores of the shell. In the northern 

 shell the pores are so small and open so close to the surface as to be 

 sciircely visible to the naked eye, and are mostly scattered singly with 

 but little grouping. Hence the surface appears almost uniformly smooth. 

 though fine pores can be detected with a lens. In the southern egg the 

 shell pores are larger, sunken below the general surface and mostly in 

 small groups, varying from about six to twelve in a group. It is the 

 close grouping of the sunken pores which gives rise to the pitted surface. 

 In eggs which have been in the nest for some time dirt tends to accumu- 

 late within the pits and thus accentuates their presence, whereas in the 

 northern egg the \xn*'s art* ton small and shallow. Jn both ty|X'S the 



Joum. of Cren. vui 12 



