THE MASTERY OF THE AIR 263 



like a collapsed umbrella. When it is going to 

 "fly" the ribs are extended and form the sup- 

 ports of a fine parachute. The dragon can 

 swoop several yards, sometimes to avoid an 

 enemy, sometimes after a swarm of insects. The 

 upper surface of the body is brightly coloured, 

 and there is a curious dewlap on the throat. 



There is another tree-lizard, Ptychozoon, 

 whose long tail bears a scolloped fringe of 

 skin on each side, and this again helps in 

 swooping. There is a tree-snake (Dendrophis) 

 which disdains all accessories and launches 

 itself stiffly from a lofty branch to the ground. 

 But is there anything in the way of movement 

 a snake cannot do except cross a sheet of ice 

 or a horse-hair rope? 



(D) What bats achieved many mammals 

 have attempted, that is, if we regard parachut- 

 ing as on the way towards flight. It is note- 

 worthy that all the attempts at flight among 

 mammals have been made in families that are 

 arboreal in habit, so that climbing tall trees 

 may have been the first step towards acquiring 

 wings or some substitute for them. Thus we 

 have the flying phalangers of New Guinea and 

 Australia, including many species, " the largest 

 of which is as big as a cat, while the smallest 



