J. K. DlKUDKN iHf) 



In this cast' thf original |Mux?nU wen* a North AtVinin cck-U without 

 any Icmw of nailos and a South African h<»n with a Hin^h* hrcak. Of the 

 four ortHpring n'ariMl thn**' arr without the break while it «K!eurH in 

 No. 17i), the hen used in the »«xperinient. From th<* uiatiug of brother 

 and sisttT four chicka wert* hatched, two of which had two bnaks in th«' 

 scutellation. one had only a singh' break and one ha<i no bn*ak. The 

 result may Iv i\»garded jus highly suggestive that the iidi<'rcnt t<iidrncy 

 towanls the loss of scales can Ik? accentuated by in-breeding, and de- 

 generation thus accelerate<l along definite prescribed lines; for after the 

 single break the next step in the loss is a second break over the middle 

 of the t(H». In the course of the investigations it hjus become evident 

 that i\n inherent tendency exists in the ostrich towards the loss of various 

 parts of the fore and hind limbs in a continuous determinate direction, 

 as well as of it** plumage, and it is not unlikely that by in-breeding the 

 degenenitive tendency can be accentuated. The accumulation of fuller 

 data must howevtr be awaited before the suggestion as regards the loss 

 of scales can be regarded as more than tentative. 



Claw o\ Fourth Toe. 



The claw on the small, fourth toe has for the most part disiippearefi 

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

 African than on South African birds (Text-fig. 2). In 25 mixed northern 

 birds it occurred on six specimens and was wanting on the othei*s, while 

 in 20 mixed southern birds it was found on only one individual. Every- 

 where 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 can be 

 obtained!. Usually it is equally developed on both the right and left 

 foot, though sometimes a difference is observed. 



In crosses where both pirents are without the claw the progeny are 

 also devoid of it, though in a nest of IG chicks from clawless parents 

 a distinct claw appeared in one (Cross-bred No. 304). Where however 

 one parent is clawed and not the other it appears in about half the 

 progeny, showing that the clawed birds are dominant heterozygotes. 

 Out of a totid of 3(1 chicks hatched from breeding paii^s, where one 

 parent was clawed and not the other, the numbers were actually eipial, 

 18 chicks clawed and 18 unclawed. 



