ting certain
movements, by the exercise of a muscular apparatus with which their
bodies are furnished. They are distinguished from the organisations of
the vegetable kingdom by the presence of these attributes. Every one
is aware, that when the child sees some strange and unknown object he
is observing start suddenly into motion, he will exclaim: 'It is
alive!' By this exclamation, he means to express his conviction that
the object is endowed with _animal_ life. Power of voluntary and
independent motion and animal organisation are associated together, as
inseparable and essentially connected ideas, by even the earliest
experience in the economy and ways of nature.

The animal faculty of voluntary motion, in almost every case, confers
upon the creature the ability to transfer its body from place to
place. In some animals, the weight of the body is sustained by
immersion in a fluid as dense as itself. It is then carried about with
very little expenditure of effort, either by the waving action of
vibratile cilia scattered over its external surface, or by the
oar-like movement of certain portions of its frame especially adapted
to the purpose. In other animals, the weight of the body rests
directly upon the ground, and has, therefore, to be lifted from place
to place by more powerful mechanical contrivances.

In the lowest forms of air-living animals, the body rests upon the
ground by numerous points of support; and when it moves, is wriggled
along piecemeal, one portion being pushed forward while the rest
remains stationary. The mode of progression which the little earthworm
adopts, is a familiar illustration of this style of proceeding. In the
higher forms of air-living animals, a freer and more commodious kind
of movement is provided for. The body itself is raised up from the
ground upon pointed columns, which are made to act as levers as well
as props. Observe, for instance, the tiger-beetle, as it runs swiftly
over the uneven surface of the path in search of its dinner, with its
eager antennae thrust out in advance. Those six long and slender legs
that bear up the body of the insect, and still keep advancing in
regular alternate order, are steadied and worked by cords laid along
on the hollows and grooves of their own substance. While some of them
uphold the weight of the superincumbent body, the rest are thrown
forwards, as fresh and more advanced points of support on to which it
may be pulled. The running of the in