64 ANIMALS OF THE PAST 



Those who favor the jumping down theory, as 

 opposed to the jumping up, can on the contrary show 

 almost every stage in the progress from fiightlessness to 

 flight, beginning with lizards that, like the iguana, 

 jump boldly from their abiding places on the branches, 

 to the flying lemur that can sail — or parachute — for a 

 hundred yards or more. Even snakes that drop from 

 trees have developed — or there has been deevloped in 

 them — an ability to hoUow in the under side of the body, 

 which affords some slight resistance to the air. Not 

 only this, but true flight has also been developed in three 

 classes of vertebrates: reptiles, birds and mammals, in 

 the order of their appearance in time ; and if it failed to 

 develop in fishes and amphibians, it may well be 

 ascribed to the fact that neither of these groups were 

 tree chmbers and when tree frogs did appear they were 

 too highly specialized to make a success of flight. 



As to fishes, they were handicapped by the structure 

 of their fore Hmbs, and although representatives of 

 several orders have essayed to fly, only two groups, the 

 Characinidge and Exocoetidae, have met with any meas- 

 ure of success — and many people aver, that neither of 

 these really fly. 



Also it is worthy of note that none of the flying or 

 sailing animals use the hind legs actively; bats, flying 

 squirrels, even flying fish, simply use the hind limbs as 

 adjuncts to flight, holding them motionless to spread a 

 membrane or form a kitelike support for the hinder end 

 of the body. The hind legs are used to jump with, not 

 run with, save in sea birds that, like the albatross in a 

 calm, may run a quarter of a male before getting headway 

 enough to launch himself into the air. But where would 

 a lizard get a good straight away level stretch? 



The new evidence that Mr. Beebe brings forward to 

 show that flight began by sailing, consists of a series of 



