652 Do Flying Fish Fly ? [ September, 
The frequency of the fin-strokes is made the first point of 
attack. Referring to the number of revolutions made by the 
bird’s wing per second, which, according to Marey, are for the 
SPRON eke yy See Terre re Par RI Sune Abeer a ess | | 13 
Wild duck 9 
Pile oe eal un oc aa ob doce nio Anak ee 8 
Moor buzzard ....... 534 
aan aata r oo fen cee ees eon been T, 5 
Mobius remarks: “If flying fish make a still larger number of 
fin-strokes per second, then the fin-muscles must be able to con- 
tract even more rapidly than the pectoral muscles of birds and 
all other vertebrates.” Then follows a comparison of the mus- 
cles of certain fishes with those of mammals, birds and frogs, in 
respect to the time required to execute a muscular contraction— 
all with a view to showing that the muscles of Exoccetus are 
incapable of making very rapid contractions. The strength of 
this argument is impaired by two facts; first, the duration of a 
muscular contraction has never been determined for Exoccetus; 
and second, the number of fin-strokes per second has never been 
estimated, much less experimentally ascertained. 
Furthermore, it does not follow, as Mobius asserts, that if the 
flying fish make more than thirteen fin-strokes per second, its 
fin-muscles must be able to contract more rapidly than those of 
birds. That they would be more rapid than those of some birds 
under some circumstances, can be safely asserted, and nothing 
more. The number of revolutions made by the sparrow’s wing 
in a second is greatly exceeded in the wing of the humming- 
bird; and the figure given by Marey does not represent the 
maximum number of strokes of which the sparrow’s wing 1S 
capable. A complete “muscle-curve” consists of a “/aéent 
period,” a contraction and a relaxation, as every tyro in physiology 
knows, and the last two phases may vary much in duration 
according to circumstances. ke 
Again, the size of the fin-muscles is said to be incompatible 
with the theory that the fins execute true flight. 
The average weight of the entire bird, as determined by i 
Harting for thirteen birds belonging to different orders, is 6.22 
times that of the pectoral muscles. In the case of Chiroptera, 
according to the Dutch physiologist, the body weighs 13 6 times 
1« Animal Mechanism,” p. 228, 
