NINTH ANNUAL REPORT. 



221 



COMPARISON OF THE FEATHERS OF THE OSTRICH, CONDOR, AND 



EMEU 



were not absolutely necessary. Hence the extreme degeneration 

 of remiges in these birds. 



The wide web of skin filling- up the angle between the humerus 

 and the body, in the wing of the Ostrich, is interesting as being 

 perhaps a vestige of some old-fashioned patagium, functional in 

 primitive ancestors. 



C. Reef rices. — A rudder is as useless to a bird which has lost 

 the power of flight as the fin of a tadpole would be to an adult 

 frog. Thus rectrices are entirely lacking in the Rhea, Cassowary. 

 Emeu and Apteryx. In the Ostrich, there are many long, loose- 

 vaned, curling plumes representing these feathers. 



D. Body Feathers. — These have fi^llowcd three general i>pes 

 in their degeneration, or perhai)s we should say that their present 

 condition represents three more or less homologous stages. 

 These are excellently represented in the photograph, and for com- 

 parison I have chosen a secondary from the wing of a condor. 



As an example of the type showing least degeneration may be 

 taken tlu- featlu-rs of thr f )strich .'nid Rlu'.i. In .-i typical foruher 



