creature one of the most delicate and graceful of the inhabitants of
the ocean--a very model of tenderness and elegance.'

The jelly-fishes are all, in their adult state, locomotive beings.
They float freely and incessantly through the ocean, either impelled
by their own efforts, or driven by storm and billow. They for the most
part frequent the open seas, and shun the shore, their delicate frames
being endangered by the perennial strife between land and water. Being
designed for constant motion, for the navigation of the great waters,
their entire organisation is adapted to such a mode of life. We find
amongst those ocean-floaters the greatest perfection and variety of
locomotive apparatus; and they have been divided into sections,
according to the modifications of this portion of structure which they
exhibit. We shall endeavour to give a popular account of the leading
peculiarities of each, and note the most interesting points in the
history of the tribe.

In the first section, the animals are furnished with a disk or
umbrella of varying shape, which serves as a float, beneath which hang
certain processes connected with the functions of prehension and
digestion. In this division are included some of the best-known forms.
The creature, in this case, propels itself by the alternate
contraction and expansion of its disk, thus striking the water, and
driving itself forward. These movements take place at regular
intervals, and serve a double purpose. They not only propel, but at
the same time drive the water over the lower surface of the disk. Here
is situated a complicated net-work of vessels, and the fluids of the
body are thus exposed to the influence of oxygen, and receive the
needed aeration. The stroke of the disk, therefore, is not only a
locomotive, but also a respiratory act. The jelly-fishes of this
section move as they breathe, and breathe as they move. Hence the name
which has been given them--_Pulmonigrades_. We find the same admirable
economy of resources amongst the lower animalcules. The cilia which
propel them secure the aeration of the system.

It is evident that the motive apparatus in this section of the
_Acalephae_ is but a feeble one. It only avails in calm weather. When
the sea is agitated, the jelly-fish is driven helplessly along. It
cannot choose its path. As its food, however, is everywhere abundant
around it, and it has no business that should lead it in one direction
more than another, there