THE CANADIAN NATURALIST. 



animals proceed by running, as the horse, the partridge, the 

 Cicindela ; some by leaps, made by the elastic force of the 

 hind feet, as the kanguroo, 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 Medusae: 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 (Physalis) : 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. 



