S().\[li KESL'LTS OF OSTKRll I N VESTIGATK^NS. 263 



Tabli-: I. — Mcasiirciitoif of Eags of North African Ostrich. 



Long Diameter. Short [diameter. 



Series A, 1 1 eggs '">.05 5-25 



Series B, 1 1 eggs 6.24 5-43 



Series C. 14 egg^ 6.14 5 .34 



Series I). 7 eggs 6.19 5 . 37 



Average f^ . m ^.'\- 



Egg of South African Ostrich. — The egg of the southern Ijird 

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

 plentiful at the air-chamher end. hence tlie shell does not present 

 the ivory smoothness of the northern egg. A Cape hen will 

 sometimes produce a nearly smooth, round egg. but never to so 

 marked a degree as the typical Nigerian hen. Also the latter may 

 occasionally lay eggs with deeper |)ittings than usual, especially 

 in the hrst egg of the season. Among a number of eggs from 

 northern and southern birds mixed together, 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 associated with the respirator}- ])ores of the shell. 

 In the northern shell the jjores are so small, and open so close to 

 the stirface. as to be scarcely visible to the naked eye. and are 

 mostlv scattered singly, with l)ut little groui)ing, hence the surface 

 appears almost uniformly smuothi. In the sotithern egg the sliell 

 pi-)res are larger, sunken below the general surface, and mostly 

 in small groups, varying from about six t<i twelve in a group. 

 It is the close grouping of the sunken pores which give rise to 

 the pitted surface. In eggs which have been in the nest for some 

 time dirt tends to accumulate within the pits, and thus accentuates 

 their presence, whereas in the northern egg the pores are too 

 small and shallow. In both types the outer enamel layer shows 

 differences in thickness, and with it the polished character of 

 the surface. All the eggs are a cream or y^'lov/ colour when 

 freshly laid, but fade considerably on exposure. 



Twii series of measurements, of 10 eggs cach, have l)een 

 obtained, and the averages are as follows: — 



Tai'll. 2. — Mcasitremcnt of Eggs of South African Ostrich. 



Long Diameter. Short Diameter. 



Series A, 10 eggs 5-92 4-<^S 



Series B, 10 eggs 5-93 5 -OO 



Average S.92 ^-92 



With such variable structures as eggs a larger series of 

 measurements is desirable in order to seciu-e a more relial)le 

 average. They serve to show, however, that on the average the 



