474 ON THE FLIGHT OF FLYING-FISHES, 



are directed outwards and backwards. Towards the end of the 

 flight the hind wings are somewhat suddenly advanced (text-fig. 2). 

 They still remain extended in the horizontal plane. The effect of 

 this movement is to bring the lift of the wings as a whole further 

 forward in respect of the centre of gravit3^ The fish consequently 

 rotates round its transverse axis. It is a rotation upwards, 

 i. e. the head goes up, the tail down. The angle of incidence of 

 the fore wings is consequently increased to such an extent that 

 their plane assumes a large angle with the direction of flight. 

 Consequently they present great resistance to speed .ahead. The 

 speed rapidly decreases and the fish drops. The tail is the first 

 part to be immersed, and the animal falls in with a, very small 

 amount of splash. 



7. Termination of flight ivithoict checking speed. 



A species of flying-fish is known to me which is of small size 

 and which generally appears in groups of eight or ten individuals. 

 They do not, as a I'ule at least, fly either so far or apparently so 

 fast as individuals of other species that have come under my 

 notice. Their flight also differs in two other respects. First, 

 they usually fly in a straight line and do not follow the water- 

 surface as is generally the habit with other species. Secondly, 

 at the end of their flight they steer downwaixls by retiring the 

 wings through an angle of about forty-five degrees. They then 

 plunge head foremost into the water without any visible attempt 

 to check their speed. 



It is possible that this species is identical with Exocmtus evolans. 

 This is the name of a species, or of a group of closel}^ allied 

 species, which differ from other flying-fishes in that their pelvic 

 fins are small and placed far foi'wa.rd. Hence these fins are 

 unfitted to function either for checking speed or for steering in 

 the vertical plane. 



It is probable that the frequent shortness of the flights of 

 flying-fishes is often involuntary. My observations indicate that 

 flying-fishes sometimes behave as if they had made a mistaken 

 estimate of the suitability of the air for their flight. On one 

 occasion I noticed that they were starting with their wings 

 disposed for slow-speed flight, that they immediately changed over 

 to the high- speed disposition and then, at once, fell into the 

 water with a splash. On my recent voyage I noted, on one 

 occasion, that flying-fishes were starting witli tails up {i. e. as in 

 high-speed flight). They then, either at once fell into the water 

 or lowered their tails and flew on. On other occasions when 

 groups of small individuals emerged they all at once fell in with 

 splashing or, in some cases, while the rest splashed in, one or two 

 got away and made flights of normal length. 



