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ubject well worth the consideration of the naturalist: the soaring of the Birds of Prey,--the heavy flapping of the wings in the Gallinaceous Birds,--the floating of the Swallows, with their short cuts and angular turns,--the hopping of the Sparrows,--the deliberate walk of the Hens and the strut of the Cocks,--the waddle of the Ducks and Geese,--the slow, heavy creeping of the Land-Turtle,--the graceful flight of the Sea-Turtle under the water,--the leaping and swimming of the Frog,--the swift run of the Lizard, like a flash of green or red light in the sunshine,--the lateral undulation of the Serpent,--the dart of the Pickerel,--the leap of the Trout,--the rush of the Hawk-Moth through the air,--the fluttering flight of the Butterfly,--the quivering poise of the Humming-Bird,--the arrow-like shooting of the Squid through the water, --the slow crawling of the Snail on the land,--the sideway movement of the Sand-Crab,--the backward walk of the Crawfish,--the almost imperceptible gliding of the Sea-Anemone over the rock,--the graceful, rapid motion of the Pleurobrachia, with its endless change of curve and spiral. In short, every Family of animals has its characteristic action and its peculiar voice; and yet so little is this endless variety of rhythm and cadence both of motion and sound in the organic world understood, that we lack words to express one-half its richness and beauty.
IX.
The well-known meaning of the words generic and specific may serve, in the absence of a more precise definition, to express the relative importance of those groups of animals called Genera and Species in our scientific systems. The Genus is the more comprehensive of the two kinds of groups, while the Species is the most precisely defined, or at least the most easily recognized, of all the divisions of the Animal Kingdom. But neither the term Genus nor Species has always been taken in the same sense. Genus especially has varied in its acceptation, from the time when Aristotle applied it indiscriminate