FLYING FISHES AND THEIR HABITS. 499 



wings weigh, on an average, one-sixth of the total weight of the body, 

 the pectoral muscles of bats one-thirteenth, the muscles of the i)ectoral 

 fins of flying fish only one thirty-second. The impulse to which 

 flying fish owe their long shooting passage through the air is deliv- 

 ered while they are still in the water by the powerful masses of mus- 

 cle on both sides of their body, which are of mucli greater lireadth 

 than in the case of the herring or any other fish of their OAvn size." 



The movement of the pectoral fins, described generally as flickering, 

 vibrating, or flapping, " is only a vibration of their elastic membrane, 

 and is to be referred to the same laws as those which govern the 

 flapping of a tight-set sail when a ship under a stiff breeze is driving 

 close to the wind. The flapping or vibration at once springs up 

 whenever the sail gets parallel to the wind. 



" The more rapidly a flying fish darts out of the water the greater 

 is the momentum Avith which the air presses on the outspread pectoral 

 fins. Should, now, the atmospheric pressure induce these fins into a 

 horizontal position parallel to the wind their vibration is a necessary 

 result. Let the outspread jDectoral fins of a dead flying fish be held 

 horizontally before the opening of a pair of bellows and the fins will 

 be seen to vibrate as soon as the current of air passes under them." 



Such are the conclusions enunciated by Mobius in a special memoir 

 (in German) on the movements of flying fish through the air( 1878) 

 as epitomized in 1885. These, however, were vigorously objected to 

 by C. O. Whitman (1880), who urged, "Admitting that in form, 

 size, length, and structure the pectoral fins of Exocoetus 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 capal)le of executing true flight." 



Opposed to this view are the expressed opinions of many distin- 

 guished traveler-naturalists. Moseley, who circumnavigated the 

 globe as naturalist of the great Challenger Ex[)edition, exi)ressly 

 declares that he had "• never seen any species of ExocoetKs flap its 

 wings at all during flight. These fish merely make a bound from the 

 w^ater and skim, sui)ported by their extended fins, the tips of which 

 meanwhile quiver in the air occasionalh' from the action of air cur- 

 rents against them, and sometimes from the shifting a little of their 

 inclination l)y the fish." Jordan and Evermann (180()), who had 

 many opportunities for observation *' under most favorable condi- 

 tions," were convinced that " no force is acquired while the fish is 

 in the air. On rising from the water the movements of the tail are 

 continued until the whole body is out of the water. While the tail 

 is in motion, the pectorals. seem to be in a state of rapid vibration, 

 but this is apparent only, due to the resistance of the air to the motions 

 of the animal. While the tail is in the water the ventrals are folded. 

 When the action of the tail ceases, the pectorals and ventrals ai'e 



