No. 627] GERM PLASM OF THE OSTRICH 331 



having with a large measure of independence. The losses 

 are continuous for the race but discontinuous for the indi- 

 vidual; and it is with the individual that heredity is con- 

 cerned and evolution with the race. 



The degeneration phenomena presented by the ostrich 

 in connection with its wings and legs, as well as with its 

 plumage, would appear to provide us with an example of 

 the application of mutative and Mendelian principles to 

 such evolutionary facts as confront the comparative anat- 

 omist and paleontologist. So far as concerns the indi- 

 vidual bird the retrogressive changes are shown to occur 

 as separate mutations and to follow definite factorial 

 lines, while as concerns the evolution of the race they pro- 

 ceed in a continuous determinate manner. In all prob- 

 ability they take place wholly irrespective of any adaptive 

 significance or consideration for the welfare of the bird, 

 and are intrinsic in their nature and uninfluenced by ex- 

 ternal conditions. Natural selection has probably played 

 no part in connection with the losses, for the greater 

 changes have already affected the race uniformly and the 

 smaller ones which still vary in degree in different indi- 

 viduals will probably affect the whole in the end. Should 

 the loss of plumage continue to a much further degree 

 and marked degenerative changes be set up in the big 

 middle toe natural selection may then be expected to bring 

 about extinction. 



The chief point desired to establish at present is that 

 as regards the number of its wing plumes and in certain 

 other features the ostrich affords strong support for the 

 view that its hereditary determiners or factors are chang- 

 ing regularly and frequently ; they are not fixed and con- 

 stant as are the factors for the structural details of the 

 plumes ; one series is in a stato of cliaiiiio. tlie other is non- 

 changing. The great variety niul (Icmcc of the degenera- 

 tive stages in the ostrich of to-day admits of no question, 

 and that they are the expression of so many germinal 

 differences may be accepted, seeing that they breed true; 

 that they have been effected simultaneously as we find 



