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 aswarm 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 stiffy 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 
