FLYINO FISMES AXF) I'll KIR HAIUTS. 499 



Winers woiffh, on an avorao^o, one-sixth of the total Avoifjht of the body, 

 Iho pectoral muscles of bats one-thirteenth, the nnisoles of the pectoral 

 fins of flvinii: fish onl}' one thirty-second. The inipidse to which 

 flyin<r fish owe their lono- shootinjj passafft" throuo;h 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 much greater breadth 

 than in the case of the herring: oi' s^w other fish of their own 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 ^^ind. 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 mortientum with 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 pectoral 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 epitouiized 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 Exoca'tus are less well 

 adapted to flight than the wings of most birds, there is still ami)le 

 room to l)elieve, on anatomical and physiological grounds alone, that 

 they are capable of executing true flight." 



Opposed to this view are the exj^ressed opinions of many distin- 

 guished traveler-naturalists. Moseley, who circumnavigated the 

 globe as naturalist of the great Challenger Expedition, exi)ressly 

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

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

 water and skim, supported by their extended fins, the tips of which 

 meanwhile quiver in the air occasionally from the action of air cur- 

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

 inclination by the fish." Jordan and Evermann (1896), Avho 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. "\Miile 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 Avater the ventrals are folded. 

 AVhen the action of the tail ceases, the pectorals and ventrals are 



