1909] Beebe: Tail Feathers of the Motmot. 149 



affected by this degeneration, and thus brings about the remark- 

 able, symmetrically formed rackets. If, as seems inevitable, we 

 must take this view of the phenomenon, the fact of the narrow- 

 ing of the vane at the later denuded portion, requires no "in- 

 heritance of acquired character" explanation, but takes its place 

 as one of several features of degeneration — ^the original cause 

 of which is as yet unknown to us. 



I come to these conclusions rather unwillingly, as ever since 

 my intimacy with Motmots in the field in Mexico,* I have always 

 held these birds in the highest regard, especially for this inex- 

 plicable feat of self -decoration. 



My conclusions have been forced by the following facts : 



1. If considered as a voluntary congenital habit, the fact 

 that it is absolutely unique and inexplicable. 



2. The presence of the phenomenon in both sexes. 



3. The absence of individuality in trimming, resulting in 



4. Physiological accuracy in all instances. 



5. Lack of special attention paid, in preening, to the racket 

 feathers. 



6. The extreme degeneration of the area, and consequent 



7. Fragility of the barbs. 



8. The present narrow limits between actual physiological 

 denudation in the sheath, and ultimate preening-denudation. 



Further work with a number of living birds, Motmots and 

 Parrots, will do much to clear the field of negative factors, leav- 

 ing the bare facts of physiology and habit to be correlated with 

 the ecological conditions of life, in this and related problems. 



'Two Bird-lovers in Mexico," pp. 198-204. 



