somf. resi'lts of ostrich investigations. 2/1 



Degeneration in the Ostrich. 



The Ratitre, or running birds, to which the ostrich belongs, 

 are looked upon as degenerate in many respects compared with 

 the Carinat?e, or flying birds, jDarticularly as regards tlie wing 

 which is no longer of use for flight. The ostrich is also unique 

 among birds in having only two toes to the foot, in place of the 

 usual four. The large number of northern and southern birds 

 now available for study has disclosed many other directions in 

 wliich a loss of parts is taking place, and the various stages in the 

 degenerative process obtainable, serve to indicate the manner 

 according to which the losses are effected. Independent lines of 

 degeneration are exhibited by parts of the plumage and the digits 

 of the wing and foot, and are here briefly summarised. 



Under-C averts. 



First Row. — In nearly all ostriches only a single row of 

 imder-coverts occurs, and this is rarely a complete row. (PI. 5^.) 

 The members alternate with the row of wing quills, and also with 

 the last plume of the first, second, and sometimes third row of 

 upper-coverts which, along with the remiges, constitute the mar- 

 ginal row of plumes. Only in two birds out of hundreds examined 

 has the full alternation of under-coverts been observed, and often 

 as many as nine or ten are missing. The absent members are in 

 regular succession, beginning at the elbow end of the row. All 

 stages in the loss can be procured, though the greater number of 

 ostriches have from seven to ten missing. Actual countings of 

 25 birds gives an average of 30.2 coverts, which is six less than 

 the average of the remiges, and two or three more should be 

 present for alternation with the last member of the rows of upper- 

 coverts. 



While usually the losses are entire plumes, not infrequently 

 two or three vestigial feathers are seen beyond the last ordinary 

 member of the row. These are not simply diminutive feathers, 

 but are imperfectly formed, the axis especially being imperfect. 

 The degenerative stages are similar to those better seen in connec- 

 tion with the down feathers on the wings and tail, where it is 

 found that the shaft is the first part to break up and disappear, 

 then the barbules, and lastly the barbs. The vestigial feathers 

 continue to appear with the regular succession of the plumages, 

 but are more prone to disappear with age than the normal 

 feathers. 



From the details submitted it is evident that the row of 

 under-coverts in the ostrich is in process of gradual reduction, 

 beginning at the elbow end. The number of birds available makes 

 it possible to trace all the stages from the complete row to where 

 as many as ten have disappeared, showing that the process does 

 not proceed uniformly in all the representatives of the race. In 

 most cases the loss involves complete feathers, though the presence 

 of the vestigial members indicates that it takes place in ])iecemeal 

 fashion, according to a definite sequence. 



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