266 SOME RESULTS OF OSTRICH INVESTIGATIONS. 



ostricli which will be of practical importance to the breeder in 

 the future, and which are also of some scientific interest from the 

 point of view- of the evolution of the ostrich. From the facts and 

 ])rinciples presented it should be possible for farmers to increase 

 by as nmch as 25 per cent, their output of feathers from the same 

 inunber of birds, or, a more desirable consequence, to procure 

 the same quantity of plumes from three-quarters of their present 

 number of birds. 



North African Ostriches. — The first-row feathers on each 

 wing have been counted on 25 of the original imported North 

 African birds, and the results are given below. It will be noted 

 that a difference of one or two plumes is often found between 

 one wing and the other, but the cocks and hens show no distinc- 

 tion. The number on the wing varies from 33 to 39, the arith- 

 metical mean of the series being 36.34; rei)resented graphically 

 they approximate to a normal frequency curve with the mode at 

 36. Manifestly the birds represent a mixed population, a result 

 of indiscriminate breeding in a race in which the numbers differ 

 by small amounts ; but indications are not wanting that a pure 

 line can be built u|) of each number. We may regard each bird 

 as heterozygous with regard to number of plumes, and a mixture 

 of the kind given below is what would be expected, seeing the 

 birds come from a single area in North Africa, where no farming 

 selection has been i)ractised. 



Table 4. — First-rozv Plumes on Winys of Imported North 



African Ostriches. 



The number of plumes on the wings oi 15 pure Ncjrth 

 African chicks, reared at Grootfontein from the importation, are 

 also re])resented. and give approximately the same arithmetical 

 mean as the above, namely 36.7, though without the low numbers 



33 ^^^'^^ 34- 



