Xo. 627] GERM PLASM OF THE OSTRICH 



319 



which he desires to see in combination in their progeny, 

 but he never dreams that any change in the characters 

 themselves will result therefrom. Though perhaps un- 

 able to express it in words he knows that the germ plasm 

 of each of his birds contains so many factors, and in his 

 selection of breeders picks out the birds having the 

 factors he desires to give him new combinations, but he 

 has no expectancy that the factors themselves will 

 undergo any change as evidenced by their expression in 

 the progeny. Selection along the prescribed lines is prob- 

 ably as rigid as that which any experimentalist could 

 carry out, and is certainly more so than can be conceived 

 of as taking place in nature, yet long as it has been in 

 operation it has never carried with it an alteration of any 

 of the existing diversities of plumage. 



IV 



''When the germ plasm changes it does so as a result 

 either of wholly internal physiological causes, or of very 

 extraordinary environmental stresses acting directly upon 

 the germ cells. ^' 



The bodily charactci s of the Smitli African ostrich pre- 

 sent a remarkable niii ('(u iiiity cxcejtt as regards certain 

 details to be describ(Ml later. Imt in comparison with the 

 North African liird i)ian> striking differences appear. In 

 1912 the novc^iiimciit d' tlie Union of South Africa im- 

 ported 132 .-]HcinuMi> of the northern ostrich from 

 Nigeria. It was hoped that in these some one or other of 

 the plumage characteristics might be developed to a 

 higher degree than in the southern bird and could with 

 advantage be combined with the latter. Experiments 

 with this end in view are now in progress under the direc- 

 tion of the writer. 



The northern ostrich is longer in the legs and neck than 

 the southeni, the head reaching a little over eight feet 

 from the ground, about a foot more tlian in tlio latter. 

 The color of the skin of immature birds of l)(»tli -i'xr< and 

 of mature hens is a creamy yellow, while the niaturi' cock 



