164 Degeneration in the Ostrich 



groups at a time, giving rise to one or more breaks in the course of 

 the row. In this case the seven to ten distal scales on the fourth toe 

 do not represent the survivals of a larger series which has retrogressed 

 one at a time from the original proximal end of the row, but a group 

 which has not yet entered upon a degenerative phase ; and it by no 

 means follows they will retrogress singly, as would ordinarily be expected 

 for meristic structures. 



Already the claw on the fourth toe has for the most part disappeared 

 from the race, though it is occasionally present, more often on North 

 African than on South African ostriches. In 25 mixed northern birds 

 it occurred on six specimens and was wanting on the others, while in 

 20 mixed southern it was found on only one. Everywhere it is feebly 

 developed, especially by comparison with the big claw on the middle 

 toe, and is always non-functional, never reaching the ground. Where 

 best formed it projects for about half an inch from its socket, while at 

 other times it is almost hidden in the integument, and can scarcely be 

 felt with the finger ; but all intermediate sizes between the extremes 

 can be obtained. Usually it is equally developed on both the right and 

 left foot of the same bird, though sometimes a difference is observed, 

 or it may even be present on one side and absent from the other. In 

 the present reduced state of the digit no adaptive significance can be 

 attached to the presence or absence of the claw, and therefore natural 

 selection is in no measure influencing its retrogression. 



It may be observed that such a simple distinctive structure as a 

 claw is easily seen and compared on different individuals, especially on 

 young chicks which can be closely handled. The relative sizes readily 

 admit of a grouping into strong, medium, weak and integumental, 

 though without any sharp line of separation among them. As it is 

 altogether functionless, never reaching the ground, any variation may 

 be taken to represent a germinal as compared with an environmental 

 change, and as due to intrinsic rather than extrinsic influences — a con- 

 clusion particularly convincing when a marked difference is apparent 

 on the two sides. Moreover, the variations are just as conspicuous on 

 newly-hatched or even unhatched chicks as they are on older birds. 

 Since the claw is so frequently absent and varies so much in its 

 development on different birds, it may be presumed to be in a highly 

 degenerative phase at the present time. The results from the 

 various breeding experiments are in like measure strongly suggestive of 

 degradation being in progress, and will therefore be given in some 

 detail. 



