326 Transactions. — Zoology. 



\\ hat, until more information is obtained, must be regarded as 

 their correct position (fig. 4). Fig. 5 shows the under-side 

 of the same wing. I then extended the wing, and after several 

 experiments found that, by manipulating the joint with tlie 

 fingers just before the wing became fully stretched, most of 

 the primaries could be made to take the position they occupied 

 when first examined — that is, the locked position (fig. 2). 



This seems to prove that the bird had the power of, at will, 

 altering the relative positions of these feathers. If such a sup- 

 l)osition can be placed beyond doubt it will give a decided 

 indication of the reason for their peculiar outline, and maj' 

 perhaps throw much light upon the still-vexed problem of 

 fiight ; for it would appear that this locking, 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 otlierwise be imposed upon the wing- 

 muscles during soaring — a strain wdiich various experiments 

 have shown would be very great — indeed, almost insupport- 

 able — unless the muscles were relaxed at short intervals; but, 

 as birds sometimes remain soaring for hours, it is evident that 

 no such relaxation or flapping takes place. I am aware that 

 the partial change in the position of the primaries would seem 

 to lessen the resistance which the expanded wing could give to 

 the air ; also, that all soaring-birds do not possess notched 

 feathers, and that some birds which do not soar have them. 



I have not had the opportunity, nor do I possess the skill, 

 requisite to minutely examine the internal structure of the 

 wing, but feel sure that, although the anatomy of wings has 

 received great attention, and is apparently well understood, it 

 will yet be found that there is some muscle either set apart for 

 the purpose of altering the position of these feathers in the 

 manner indicated, or one the secondary function of which is 

 to do so. 



The whole question can only be decided 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 an 5^ pretence to settle the matter, 

 but with the hope that others who possess more facilities for 

 conducting experiments and research may be induced to study 

 the subject. Then, perhaps, a satisfactory solution may be 

 discovered. 



