478 THE ZOOLOGIST. 
portant to observe that Mébius has here affirmed an identity 
without any authority whatever. He shows his deference to the 
statements of ‘‘ good observers ” by undertaking to sweep all their 
testimony out of court by the mere breath of his private opinion. 
Surely this is a most facile mode of reconciling contradictory 
testimony ! 
If Mébius merely announces it as his opinion that the 
tremulous movement observed in his experiment is identical with 
the movement that has been so often interpreted as a true flying 
movement, then we have simply to raise objections. 
There are three questions here to be considered: 1st, whether 
the fins probably exhibit such movement; 2nd, whether such a 
movement, if made, would be probably recognised; and 38rd, 
whether, if recognised, it would likely deceive ‘‘ good observers.” 
It would seem that the wings of a sailing-bird, such as a Gull 
or a Hawk, would be quite as likely to exhibit such motion as the 
fins of the Flying-fish ; and it would be much more easily recog- 
nised in the former than in the latter. 
With reference to this point I watched the long-winged Gulls 
that were seen almost every day of our voyage. These birds 
were often circling about the stern of the boat on the watch for 
waste bits of food, and were remarkably good skimmers, moving 
the most of the time without flapping the wings. I very rarely 
saw any vibratory movement that could be attributed to the wind 
alone, and never anything of the kind that was of more than a 
momentary duration. It is very evident that, under conditions 
that would render possible a continuous movement of this kind, 
the bird, as well as the fish, would inevitably fall to the water. 
Is it probable that a momentary quiver in the comparatively 
small fin-wings of a swiftly-moving Flying-fish would be 
noticed? The fact that no naturalist has ever affirmed anything 
of the kind except Mobius, who bases his assertion on an 
experiment with an alcoholic specimen, is sufficient answer to 
this question. 
As to the probability of any one being deceived by such 
motion, I cannot, of course, judge from experience, as I have 
never been so fortunate as, in the first place, to detect it, and, in 
the second place, to discover that I had erroneously interpreted 
it. I cannot persuade myself, however, that any ‘‘ good observer ” 
would be likely to make such an egregious blunder. 
