CTENGPHORES. 
475 
ever, such as the sea-anemones and the jelly-fish, have no hard skeleton at all, but 
are amongst the most delicate and beautiful objects in the realm of living nature. 
In spite of the variety of forms to be found, the Ccelenterata are almost as 
incapable of higher development as the Echinoderms. Like the latter, they have 
failed to make any way in fresh water, not to speak of the land. A few free- 
swimming jelly-fish, a minute attached polyp, and some degenerate sponges are, 
indeed, found in fresh water, but these can hardly be looked upon as successes. 
While, at present, it is not easy to connect the Coelenterata with any other group, 
inasmuch as they appear to stand without any near relatives among the higher 
animals, they have a special interest, since they are considered to represent a stage 
in the development of animal life through which all the higher forms have passed. 
Some simple form of Coelenterate may have given rise to all the higher animal 
forms, the modern Ccelenterates—the sea-anemones, corals, etc—being those 
descendants of the primitive simple form which have retained the original type of 
organisation almost unchanged. 
The Ctenophores, —Group Ctenophora. 
Although all are agreed that the so-called Ctenophores are members of this 
subkingdom, their exact position is not clear. The Ctenophores are glassy, 
transparent creatures, either shaped like apples, melons, or Phrygian caps, or else 
forming bands, often a yard in length, and thickened at the middle. Several 
types are shown in the coloured Plate. The marvellous transparency of all 
but one ( Beroe ) is specially remarkable. They inhabit the open sea, or are driven 
by currents and winds near the coast and into harbours. Their position in 
the water is usually more or less vertical, the mouth being turned downwards. 
The organs from which this group takes its name are the ribs, which either run 
from pole to pole, or else only for certain distances along the meridians, which are 
often symmetrically arranged. These ribs consist of rows of short transverse 
combs, each being formed of a row of cilia. The cilia forming a comb are connected 
together at their bases, but are also capable of independent movement. As they 
wave to and fro, they constitute what is called a swimming or rowing plate. The 
activity of these rows of plates depends upon the will of the animal, which can 
move either the plates of a single rib, or all the ribs together; this latter movement 
resulting in slow locomotion in the direction of the apical pole, i.e. the pole turned 
away from the mouth. The body is capable of various swift, light, and graceful 
movements, for in addition to the rowing plates there are other structures, such as 
the oral umbrella and the capturing filaments or tentacles, with their hair-like 
branches. These tentacles, which are attached like arms at the sides, are capable 
of erection, or of withdrawal into pockets. There is great variety in the develop¬ 
ment of these accessory organs of locomotion. For instance, the Cydippidce 
have only arms, which, with their branches, serve for capturing food as well as 
for steering. In other orders, vertical, oar-like, dermal folds stand out from the 
body, by means of which the movements become more rapid and energetic. Some 
species of Eucharis, by suddenly shutting up the oral umbrella, can jerk themselves 
forward; and when successive jerks of this sort cause the body to move with 
