flies disported themselves in the summer sun, amid landscapes 
that would seem strange to our eyes. For there were no trees 
and flowering plants, such as we know. 
The dragon-flies of that remote epoch were very like those of 
to-day, whose dancing flights and graceful, swooping movements 
are such a delight to watch by reed-fringed pools, or river-banks, 
during the sweltering days of summer. This flight is very 
different from that of a bird, though it would be hard to say 
precisely in what it differs. But we have no such difficulty in 
regard to the broad outlines of the mechanism of such flight. 
To begin with there are two pairs of wings, and these appear to 
be fashioned out of some curiously gauze-like material, a sort of 
mesh-work tissue, often strikingly coloured. And they are 
obviously driven after a very different fashion from those of the 
bird. For in the bird they are moved by quivering muscles, 
attached to a bony, internal skeleton. In the dragon-fly—as 
with all insects—the hard skeleton, composed of a material 
known as ‘“ 
chitin,” forms the outside of the body and encloses 
the muscles. Finally, for we may not dwell very long over this 
aspect of flight, it is clear that the wings cannot have been derived 
from modified fore-legs, like those of the bat, or the bird. 
Rather, it would seem, they have developed out of plate-like 
breathing organs. 
