178 Crossing the North and South African Ostrich ' 



A hint- at factorial purity is indicated seeing that the extremes 33, 34 

 and 39 are not represented. 



TABLE YII. 



dumber of first-row Plumes on Cross-bred Chicks from mating a 

 North African cock with a South African ken. 



Parents : 



North African cock, No. 78 

 South African hen, No. 225 



Survival of ^2-plumed Ostriches. Among the Cape birds in the 

 Grootfontein flock two^ have been discovered with 42 plumes to the 

 first row, though the rest have the usual average of about 36. At first 

 it seemed as if two distinct strains of ostriches were represented in 

 South Africa, as compared with the single strain in North Africa, one 

 with approximately 36 plumes as the average and another with 42. 

 The countings on farmers' birds have however given no support for this 

 view ; they have disclosed no individual bird exceeding 40 plumes, nor 

 any influence from a 42-plumed strain. Hence it is concluded that the 

 occurrence of ostriches with 42 plumes is altogether exceptional among 

 Cape birds, and has had no recent influence on the general average. 

 Likewise none of the Nigerian birds has more than 39 plumes, nor any 

 of the chicks reared from them ; so the influence of a 42-plumed strain 

 is non-existent in North Africa. 



As regards their origin it is manifest that the 42-plumed birds re- 

 present a distinct departure from the ordinary 86-plumed birds. Were 

 no other evidence available the high number might be looked upon as 

 a meristic mutation and, as will be proved later, the birds give progeny 

 with such high numbers as to show that the extra plumes are not merely 

 the extreme limit of a fluctuating series but have a factorial value. They 



' Of the two original birds one has since met with an accident and died. The birds 

 were procured several years ago from two farmers widely apart, without any suspicion of 

 their number of plumes. It is noteworthy that though search had since been made among 

 the same flock yet in neither case has another 42-plumed bird been found. 



