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THE AMERICAN NATURALIST [Vol. XLI 



the fish could never arrive at a speed by which a very short aero- 

 plane flight could be attained even with their low ratio; but I do 

 say that such is not their common speed, and that in any case their 

 disregard of wind-direction disproves such flight. 



Therefore another way must be looked for, and we are driven 

 back, perforce, to continuous wing-action, the manner of which 

 may be here examined as carefully as our information allows. 



Premising that the flight varies greatly on different days and 

 under different conditions, the following is probably a fair descrip- 

 tion of their methods in an ordinary flight: — 



1. The tail-impelled, visibly (to many) wing-assisted jump 

 from the water to a height where the wings can work freely. 



2. The flight continued by an intensely rapid and labored 

 w^ing-movement — one easily mistaken for stillness, and usually 

 seen, if at all, as blur. 



3. Short periods of slowing down of wing-speed, during which 

 the wing-movement becomes again visible. (These are the "vibra- 

 tion" periods, representing to aeroplanists loose wing-trailmg, 

 or dragging like a flapping flag — an impossibility; and, to Mr. 

 Adams, periods of wing-assistance — with limitations a possibility.) 

 These periods often precede a special spurt such as is re(|uired to 

 lift the fish over an oncoming wave. 



4. Either sudden cessation of wing-mo vcukm it and consctiuont 

 immediate drop into the sea or a short slow down into visibility 

 (No. 3) previous to such drop. 



It is to be noted that this vibration so often seen before the fish 

 enters the water is one of the many pointers to continuous wing- 

 movement, for such a time is a proper one for slowing down, but an 

 absurd one for renewal of wing-effort. 



To return to Mr. Adams's paper. He notes, as have others, 

 the vibration of the wings as being in "an almost horizontal direc- 

 tion." This horizontal movement, if it exists, as is probable, 

 may afford, as I hope to show, a looked for key to the fish's action. 



According to Pettigrew, it is a necessity of flight, where wing- 

 beats are in a more or less vertical direction, that the up-beat should 

 meet with little and the down-beat with much resistance from the 

 air. This is arranged for in the case of bats, birds, and certain 

 insects by means of special muscles and ligaments which automat- 



