1909] Beebe: Tail Feathers of the Motmot. 143 



much, with head drawn in and eyes shut, that I was alarmed. 

 An examination showed, however, that the bird was in fair con- 

 dition and would undoubtedly live through its moult. At this 

 critical time I again plucked the long tail feathers which, by their 

 bedraggled condition, showed the lack of care due to the moult 

 illness. Daily I watched for the new incoming feathers, and 

 daily the blood sheaths grew longer. Finally, when they were 

 about four inches in length, the drying sheath began to crack 

 and fray off, releasing the folded vane within. 



When this natural unsheathing had proceeded for several 

 days, a portion of the feather appeared disarranged. When the 

 sheath broke from this part, the fact was made plain that the 

 disordered appearance was due to part of the web coming away 

 with the sheath, and the irregular breaking off of the latter made 

 the separated barbs stand out in all directions before being lost. 

 When the feathers grew out still more, it was seen that above the 

 rackets the regular denuded portion of the shaft was as bare as 

 if the Motmot had stripped it. This was an interesting result 

 and is probably explained by the low vitality of the bird and the 

 severe strain on its plumage-producing resources causing a les- 

 sened and insufficient nutrition in the development of these long 

 feathers. The radical result of the physiological loss of the vane 

 is to be interpreted by the existence of an actual weakened condi- 

 tion of the bases of the barbs of the normally trimmed area, 

 which was intensified under the influence of the moulting illness 

 in this captive bird. This increased weakness in the barbs took 

 the form of an actual separation, simulating the dynamic denu- 

 dation of the bird's beak. 



Whether or not this result furnishes a proof of the inheri- 

 tance of acquired characters is aside from my present thesis. I 

 wish simply to demonstrate that in the Motmot, the condition of 

 these tail feathers is such that transference of the denudation 

 from a physical act on the part of the bird to a purely physio- 

 logical process is not impossible, although at present abnormal. 



How long it would take for this process to occur normally, 

 in the evolution of this phenomenon, is of course impossible to 

 say. That it would in time advance to the condition which I 

 produced artificially is reasonable to suppose. 



Compared with the normal physical results of denudation, 

 those physiologically induced are remarkably uniform, as the fol- 

 lowing measurements in millimeters show : 



