1880.] © Do Flying Fish Fly? 649 
make themselves visible by the alternate appearance and disap- 
pearance of the light reflected from them. They would escape 
no accurate observer who viewed the fully expanded pectorals 
from the height of a steamer. But as often and as long as I have 
been able to follow with my eyes flying fish, which came out of 
the water near our boat, I have never seen light reflected in this 
manner from the pectoral fins as from the wings of birds and 
' bats” (p. 353). 
That these movements have escaped Carl Mobius is then evi- 
dent from his own testimony ; what application then is to be made 
of the statement that “ they would escape no accurate observer ?” 
This author first attempts to account for the fact that many good 
observers have affirmed the wing-like movement of the fins on 
historical and psycological grounds, asserting that this “ false 
notion” had its origin in a fancied resemblance of these fishes to 
swallows, and that it has been handed down from the times of 
Aristotle and Pliny to the present time, simply on authority; and 
afterward, as if aware that this was not altogether a satisfactory 
solution of the question, admits that these observers may have 
had some grounds for their statements, but thinks they were 
deceived by appearances, which they did not understand, into the 
belief that the fins behave like wings. He is very frank in telling 
us just what these appearances are, although no one, not even 
Mobius himself, has ever observed such phenomena in a living 
Exoccetus. 
“ Just as a sail begins to slacken and vibrate the moment the 
wind blows parallel to its surface, so the more flexible and elastic 
distal and ventral parts of the pectoral fins are thrown into rapid 
vibrations when the air-current moves parallel to their surface” 
(p. 370). 
As a simile, this will do very well, but how is it as a matter of 
fact? We are assured that this comparison is fully justified by 
the following simple experiment. A specimen of Exoceetus 
shriveled, distorted and stiffened by long soaking in alcohol, was 
Suspended and its pectorals exposed to a swift current of air in 
such a manner that the current swept along both surfaces. The 
fins thus exposed “ made directly under my eyes the same rapid 
quivering movement that various good observers of flying fish 
have regarded as a flying movement ” (p. 370-371). It is impor- 
tant to observe that Möbius has here affirmed an identity without 
any authority whatever. He shows his deference to the state- 
ments of “ good observers,” by undertaking to sweep all their 
VOL. XIV.—No, Ix. 42 
