168 Trowbridge — Interlocking of Emarginate 



(•i) It requires from ten to twenty minutes to form even 

 very slight notches artificially in the primaries of a freshly 

 killed bird. 



(5) When the notches are formed artificially by a strong 

 pressure for several hours they are not as deep as those made 

 by the natural interlocking of the primaries. 



(6) The notches found in the primaries of freshly killed 

 birds could not have been formed accidentally during the time 

 between when the birds were shot and when they were exam- 

 ined (often less than 30 seconds), but were the results of a 

 pressure due to the interlocking of the primaries acting either 

 constantly or intermittently for two or three or more hours 

 directly previous to the time when the birds were killed. 



(7) The interlocking of the primaries as an auxiliary mechan- 

 ism of flight appears to be advantageous for three reasons : 



(a) To make the end of the wing, or that part formed by the 

 primaries, more rigid when the wing is employed as an aero- 

 plane in coasting flight. 



(b) To produce a curvature of the wing which gives to the 

 bird better control in the air. 



(c) To keep the primaries partly extended without muscular 

 exertion on the part of the bird ; otherwise the air pressure 

 produced by the motion of the bird acting against the prima- 

 ries would tend to close them, unless the bird was continually 

 exerting muscular force to keep them extended. 



Confirmatory Observation in Japan. 



After this paper had been submitted for publication, a letter 

 on the subject appeared in Science* written by Professor 

 Bashford Dean describing an observation recently made by him 

 in Japan. The facts of the observation were stated with care- 

 ful detail, but only a small portion of the letter is here quoted. 



"It so happened that we were coming up the narrow canal 

 from Sakai to Matsue in the face of a strong wind, so strong, 

 indeed, that our small steamer labored to make headway 

 against it. At one point we disturbed a kite, Milvus melan- 

 otics — a very common bird, by the way, along Japanese water- 

 ways — which rose slowly in the face of the wind and after 

 making several circles followed the margin of the canal, flying 

 and soaring, almost opposite the boat and making about equal 



headway." " For several minutes the hawk 



thus flew alongside of the boat, with quite regular peri- 

 ods of flapping and soaring ; then, suddenly shifting its course, 

 it circled out, soaring, passing over my head at a distance of 

 about twenty feet. I could then see plainly that the primaries 

 * Sci. xxii, No. 564, Oct. 20th, 1905. 



