59 
Order II. 
In the Starfishes, the rows of sucker-feet are 
limited to the ventral surface. The dorsal surface 
is leathery, and beset with warts and spines. It 
likewise contains calcareous plates, though these do 
not form a skeleton, as in the Sea-Urchins. There 
are larger plates where the dorsal and ventral surface 
unite, which are often set with long spines. The 
shape of the body is always flat. 
In the typical Asterizde the body passes 
gradually into the arms, without there being any 
fixed boundary between them. This is likewise the 
case internally, for the intestines and sexual organs 
send offshoots into the cavities of the five arms. 
Fig. d. <Astertas aurantiaca may serve to illu- 
strate this family. These Starfishes feed on mollusca, 
Order Ill. 
This Order, though important in former epochs 
of the world’s history, is now limited to a few genera 
and species. The body of the animal, which is called 
the calyx, is surrounded by ten jointed and often 
branching arms. There are fine rami on the separate 
joints, which give them the appearance of feathers. 
The calyx is usually fixed on a long stalk, consisting 
of a large number of movable pentagonal calcareous 
sections, which bear whods of cirri at regular intervals. 
Fig. g. Fentacrinus caput Meduse@ is found in 


Asteroidea. 
and are disliked by fishermen, as they often destroy 
their bait. If they lose an a: n, they have the power 
of reproducing it. 
The Ophiuride possess a flattened body from 
which the arms are sharply separated; the internal 
organs are limited to the body, and do not pass 
into the arms. 
Fig. e. Ophiura lacertosa is a very active 
creature, and can force itself through the smallest 
crevice. Two of each of the chalky plates at the 
base of the arms are naked on the dorsal surface, 
and the others are covered with fine spines. 
Fig. f. Gorgonocephalus arborescens is a star- 
fish in which the arms continually subdivide into 
finer branches. 
Crinoidea. 
the West Indies, and was formerly supposed to be 
the only living representative of the group, and was 
one of the rarest and costliest ornaments of museums. 
The animals are fixed on the sea-bed by the long 
stalk, on which the body sways, surrounded with 
its delicate arms. Other species are now known, 
which live at an immense depth in the sea. 
In the genus Comatula, which inhabits the 
European seas, the animal is only fixed on a stalk 
when young, and afterwards swims freely about. 
Order IV. Holothuroidea. 
The Sea-Cucumbers have a leathery skin, 
without spines, but only with microscopic calcareous 
particles, the form of which is characteristic of the 
various genera and species. A few types of the strange 
forms which the spicules assume are here figured. 

The sea-cucumbers live on the bed of the sea, where 
they absorb the mud, and nourish themselves with 
the organic matters contained in it. The form is 
long, and the mouth is placed at one end, sur- 
~ rounded by a cluster of tentacles; the vent is placed 
at the opposite end of the body. Some species are 
dried and eaten by the Chinese under the name of 
Trepang. 
Pedata. 
These species have sucker-feet like the star- 
Family I. 

l 
fishes and sea-urchins, a more or less cylindrica 
form and a branching respiratory apparatus. 
Fig. h. Holothuria tubulosa is a common 
species in the European seas, and grows to the 
length of a foot. The sucker-feet on the ventral 
surface are flat at the ends, and those on the dorsal 
surface conical. Numerous calcareous particles are 
embedded in the skin. 
Family If. Apoda. 
These animals have neither lungs nor sucker- 
feet. They are of small diameter, but wormlike, 
and many species grow to the length of several feet. 
To this group belongs the genus Syzapta, which 
may be recognised by the calcareous particles being 
anchor-shaped. 
Family Il. Elasipoda. 
This section lives exclusively at great depths, 
and has only recently been discovered. The belly 
is flat, and the sucker-feet are arranged in rows. 
The back is usually furnished with appendages of 
considerable length. The animals are of large size ; 
but lungs are absent. 
Fig. i. Meera lucifuga is found at a depth of 
two thousand fathoms in the Atlantic Ocean, 
Subkingdom Coelenterata. 
Many of these animals resemble plants in the | When the sexual organs are mature, they generally 
beauty of their colouring, and in their being fixed | 
to one spot. ‘Their organisation is usually very 
simple, consisting mainly of a cavity which supplies 
the place of a circulatory and digestive system. 
appegy first in the form of simple groups of cells, and 
not always in the same place. Many develop a chalky 
or horny skeleton, and others remain soft. In many 
species the substance of the body resembles jelly, 
