SOME KESn/rS (IF OSTRICH INVESTIGATIONS. 261 



(Fii^. 2.) The area is roughly ])ear-shaped, l)ut ma}' be partly 

 divided down the middle. In diagnostic descriptions, the baldness 

 is considered to be a character of some importance in separating- 

 the northern species from the southern, and is even mentioned in 

 the writings of Pliny. 



The extent and shape of the naked space vary a little in 

 different ostriches, but all the North African birds at (irootfontein 

 display it to a greatc" or less degree. It is quite independent of 

 the pineal spot, and its ])Osterior border may either include this 

 ( Fig. 2), or pass in front of it. In some birds, instead of forming 

 a continuous patch, it is divided more or less down the middle, 

 having then a decided bilaterality. Often a tuft of long, hair-like 

 feathers remains at the middle of the hinder border, corresponding 

 with the tuft in the southern bird, and gradually disappears 

 forwards. The area is covered with a horny, scurfy kner, w hich 

 peels off at times, exposing a fresh, clean surface of the skin, 

 with hard bony skull immediately below. 



The baldness is not apparent in the North African ostrich 

 chick when first hatched. At that time the head is covered with 

 short bristly down as in the South African, and the character 

 becomes established in the course of the first six months or so 

 of growth. It is gradually formed by the droj)ping out uf the 

 hairy feathers from about two months onwards, and in a Ijatch 

 of chicks of the same age, practically all stages in the loss can 

 be observed, the feathers to remain longest being those of the 

 middle tuft. No shar]^ line of separation occurs between the 

 naked and covered part of the head ; a few stunted feathers 

 represent the gradual transition, while the median tuft may or 

 may not persist. No corresponding falling out of the feathers 

 ever takes place in the Cape chick. 



Naturally some interest has been attached to the l)ehavi(jur of 

 the bald ])atch in the crosses of the northern and southern ostrich. 

 ( )f the hundred or so cross-bred chicks which have been hatched, 

 none at first showed any signs of baldness, but in every case the 

 feathers began to fall out when the chick was two or three months 

 old, and at six months the i)atch was established as completely 

 as in adult North African ostriches. Thus the baldness of the 

 northern bird is shown to be dominant over its absence in the 

 southern bird. 



The two second generation chicks already reared are now 

 well over the age at which the bald i)atch becomes established, 

 and in on.e of them the head remains covered with hairy feathers 

 as in the southern birds, while in the other the baldness has been 

 formed as distinctly as in any northern bird. The F2 chicks thus 

 afford evidence that factorial segregation takes ])lace in the 

 second hybrid generation, and there can be little (luestion tha: 

 when sufficient chicks of this generation have been obtained, it 

 will be found that the baldness behaves as a homozygous dominant 

 in strictly Mendelian proportions. 



