Ill 



reason for their peculiar outline, and may perhaps throw much 

 light on the still vexed question of flight ; for it would appear 

 that this locking of the feathers together with the setting of the 

 -elbow joint, described by a celebrated naturalist, should be of 

 considerable assistance to the bird in easing the strain which 

 would otherwise be imposed upon the wing muscles during soaring 

 — a strain which various experiments have shown would be very 

 great — -indeed, almost insupportable, unless the muscles were re- 

 laxed at short intervals ; but as birds sometimes remain soaring 

 for hours it is evident that no such relaxation or flapping takes 

 place. 



It may here be mentioned that in the case of C. Gouldi, young 

 lairds of the first year do not soar, but on the contrary indulge in 

 frequent flappings, and as the primaries do not possess the well- 

 defined emarginations so conspicuous in older birds, it is evident 

 that they cannot lock the wings in the manner already described. 

 I am aware that there are apparent objections to the theory I 

 have suggested, such as that the partial change in the position of 

 the primaries would seem to lessen the resistance which the ex- 

 panded wing could give to the air ; also that all soaring birds do 

 not possess notched wing feathers, and that some birds which do 

 not soar have them. 



I have not had the opportunity to minutely examine the in- 

 ternal structure of the wing, but feel sure that, although the 

 anatomy of that organ has received great attention, and is appa- 

 rently well understood, there will yet be found some muscle 

 either set apart for the purpose of altering tlie position of these 

 feathers in the manner indicated, or one the secondary function 

 of which it is to do so. 



The whole question is one which cannot be decided save by an 

 extensive series of observations and experiments in the field, aided 

 by the most careful anatomical work in the laboratory. 



This brief note is written not with any pretence to settle the 

 matter, but in the hope that others who possess greater facilities 

 for conducting experiments and research may be induced to 

 undertake a systematic study of the subject. 



