OF INVERTEBRATE ANIMALS. 
405 
Some other forms of these gelatinous animals are worthy attention, on account 
of their beautiful colour, and the circumstance of their being capable of elevating 
themselves to the surface of the ocean, and riding proudly over its heaving billows. 
One species of this kind is called the Portuguese Man-of-War ( Rhizostoma ). 
The divisions of these animals represented by the Star-fish are composed of a 
skeleton constituted of several hundred separate pieces, and covered over with a 
thick coriaceous skin, on which are placed a number of tubercles, the tubercles 
being surmounted by spines. The pieces or plates of which the skeleton is 
composed are beautifully fitted into each other, although not all of the same 
size, and are arranged so as easily to allow of the growth of these parts. Dr. 
Grant has calculated that in the edible Echinus there are not less than ten 
thousand separate pieces composing its skeleton. 
The principal forms of these animals are very well represented by the common 
Star-fish, the Sea-urchin, and the Sea-anemone, or Actinia. The mode of 
progression amongst these animals is effected by means of suckers, with which 
they are abundantly supplied; on applying these organs to any object, they have 
the power of exhausting the air from within them, and they are thus fixed to a 
particular spot by the pressure of the atmosphere and water from without. It 
is also by means of these instruments that they lay hold of their prey, which 
seldom escapes them, if once they touch it with only one of these suckers. 
These animals—contrary to what we see generally in the Animal Kingdom— 
prey upon beings higher in the scale of organisation than themselves; they 
attack small Crabs, Lobsters, and even fish; and to enable them to consume 
such food some of them are supplied with a remarkably complicated apparatus 
of mastication, as in the Echini. 
The Sea-anemonies are perhaps the most interesting of these animals, on 
account of their shape and colour resembling the beautiful forms of the flowers of 
plants. They are generally attached to rocks at the bottom of the sea, and 
whilst expanded they assume the appearance of a richly-variegated bed of flowers, 
which would vie with the gayest and brightest ornaments of the parterre. 
With these animals one of the larger sub-divisions of the Animal Kingdom 
ends ; they are called Radiated or Cycloneurose Classes. The next sub-division 
I shall refer to is that of the Molluscous or Cyclo-gangliated Classes. These are 
familiarly known on account of the greater proportion of the animals possessing 
an external skeleton, the study of the forms of which has given rise to the 
interesting science of Conchology. 
The first among these animals is a little group called Tunicaries, and they 
seem to form a transition from the aggregated animals we have been considering, 
to those which are provided with external shells. 
These tunicated animals are more perfect in their organisation than any 
3 H 
VOL. III.—NO. XXIII. 
