.1. K. DrRKDKN 197 



the IK' Vrieaian m»nm», iiml the combiniitionH ini^ht well Im* hM Ut 

 warrant us in regnnling the two w* HfK'cifiailly cliHtinct. 



On tho other hand the birds are provi'd to interbrecKl freely, and the 

 offspring an» fertile, both inter se and with the |)arenUil foniiH. Thj* 

 fact that similar degenenUive processes — loss of pluiiuige, scales and 

 claws — an* pnK^ee<iing in both also jx)ints to a close grmiinal relation- 

 ship. In the opinion of many systcmatists the jihysiological fact of 

 fertility alone wotdd Iw deemed to justify specific unity. 



The ostrich nmges over all the habitable j)arts of Africa and there is 

 everj' likelihood that in intermediate areas between north and south a 

 mingling of the two races goes on, producing a mixed po[)ulation, com- 

 posed of all possible combinations of the two sets of chanicters. Thus 

 in the East African Ostrich, S. massaicus, as the writer has found in 

 visiting the ostrich farms in British East Africa, the colour of the hen 

 and immature cock is a cream yellow while the mature cock hjus the 

 head, neck and legs scarlet, and the birds are sijmewhat larger than the 

 southern. The bald patch is present and the eggs are pitted. The 

 Somali Ostrich, <S^. molyhdophanes, is described jvs a smaller, darker bird 

 than the southern, but the bald j^atch is wanting, and the colouration is 

 like that of the southern and the eggs are pitted. 



If the entire ostrich population of Africa were gathered together we 

 are probably justified in thinking that all intermediate forms would be 

 forthcoming between typical northern and southern birds. An excep- 

 tion would occur however in the case of the bald patch, for however much 

 inter-crossing had taken place the character would never be intermediate, 

 but would be wholly present or absent; and though the dimensions, 

 colours and eg^ characters appeared in varying intermediate degrees as 

 a result of crossing we should still have the knowledge that their distinc- 

 tive nature could be extracted by selective breeding. When discussing 

 intermediates the possibility of segregation should always be borne in 

 mind. In the present instance, where all the facts are known, inter- 

 mediate forms grading from one species to the other have no direct 

 bearing on the question of specific distinctness. Among the African 

 fauna especially, experimental breeding would probably establish that 

 many so-called species and sub-species, often founded upon one or a few 

 specimens, are in reality intermediates or hybrids of other s2>ecies. 



So long as we have the facts before us it is of small moment whether 

 we regard the northern and southern ostriches as distinct species or 

 not. It becomes a matter of individual predilection whether greater 

 importance should be given to somatic differences or to physiological 



