Ee Se 
ON THE FLIGHT OF THE FLYING-FISH. 481] 
according to the Dutch physiologist, the body weighs 136 times 
as much as the pectoral muscles; and the relation between the 
same in Hxocetus was found by Mébius to be as 32°4:1. 
If the work performed by the muscles of flight be proportional 
to the weight of the body, then, as Mébius observes, the pectoral 
fin-muscles of Exocetus must develop about five times as much 
force as the pectoral muscles of birds, and about two and one-half 
times as much as the same muscles of the bats. 
The objection from this point of view has been greatly over- 
estimated by Mobius. As Flying-fish generally move their 
pectorals during only a part of their flight, which is at most 
short, they do not need to expend so much muscular energy as 
birds and bats, which take long-continued flights. Small muscles 
may perform, for a brief period, work which only larger muscles 
would be able to perform for a long time. Mébius seems to have 
overlooked the fact that time, as well as size, is an element of 
this problem. 
Perhaps also the large air-bladder may, as Humboldt supposed, 
have something to do with lightening the work of the muscles, 
while serving as a store-house of oxygen. 
The experiment of Humboldt, by which he determined that 
the fin-rays of Hxocetus move with five times greater force than 
the rays of other fins, would seem to favour the opinion here 
maintained. Admitting that in form, size, length, and structure, 
the pectoral fins of Exocetus are less well adapted to flight than 
the wings of most birds, there is still ample room to believe, on 
anatomical and physiological grounds alone, that they are 
capable of executing true flight. 
In regard to the personal observations of Prof. Mobius, it may 
be said that they can lay no claim to the right of deciding this 
question. Whatever evidence they afford is of a purely negative 
character ; and of this fact Prof. Mobius seems to be fully aware, 
if we may judge from the stress which he lays upon other con- 
siderations. That he and others may not have been fortunate 
_ enough to recognise the wing-like motion of the pectorals, esta- 
blishes at most only a probability, which weighs very little against 
_ the positive evidence afforded by the testimony of those who have 
actually seen Flying-fish fly. 
3Q 
