342 THE CANADIAN NATURALIST. 
animals proceed by runnings as the horse^ the partridge, the 
Cicindela ; — sorae by leaps, made by the elastic force of the 
hind feet, as the kangaroo, the jerboa, the frog, the grass- 
hopper, the flea ; by a spine entering into a cavity with a 
jerk^ as the Elaters ; by a bifurcated anal spring, as the 
Podura just mentioned ; — some by flight through the air, 
performed by very different organs, the feathered wings of 
the swallow, and the skinny flaps of the bat, the transpa- 
rent filmy wings of insects, the lengthened fins of the flying 
fish, the cottony down of the Aphis Lanata^ the airy gossa- 
mer of the spider : — some hop, as the sparrow ; some walk, 
as the crow : — some move on the ground, by alternate ex- 
tension and contraction of muscular rings, as the earthworm; 
by imbricated scales, as the snake ; by a sucker at each 
extremity, as the leech ; by an application of all parts of the 
under surface to the ground, as the snail : — some swim 
through the waters, by means of fins, as fishes ; by an ejected 
stream of water, as from a forcing pump, as the grub of the 
dragon-fly ; by a serpentine motion of the abdomen, as that 
of the Ephemera ; by oary feet, as the Dytiscus and 'Noto- 
necta; by the impulse of the tail, as the lobster; by contrac- 
tion and dilatation, as the Medusce: — some glide on the surface 
of the water, as the water-measurers, and some spiders : — 
some float on the surface, as the waterfowl and the Portu- 
guese man-of-war ( Pht/salis ) : — and some slowly change 
their position by the projection of a muscular tongue-like 
organ, as the cockle, and some other Testacea. Here is great 
variety ; but doubtless there are many other contrivances for 
the same end, with which I am unacquainted. 
