Introduction. xxi 
I. Echinodermata, or sea-urchins. These animals have a leathery or 
crustaceous skin or shell, commonly covered with numerous 
tubercles. The mouth is generally in the centre of the animal, 
and is often armed with five or more pieces of bone, which serve 
as teeth ; the stomach is a loose bag ; the organs for respiration 
are vascular ; and the animals are oviparous. They are fur- 
nished with tentacular tubes, which serve as arms or feet, and 
which they can push out and draw back at pleasure ; and they 
have yellowish or orange-coloured blood, which appears to cir- 
culate. Cuvier divides this class into those with feet, and those 
without; but Lamarck, whose arrangement has been more 
generally followed, divides them into three orders ; viz. : 
1. The Fistuloides, or Holothurida, which have cylindrical bodies, 
leathery skins, and mouths surrounded by tentacula. These 
creatures live in the sea, or in the sands on the sea-shore ; the 
trepang, or eatable worm of the Chinese, is one of them. 
2. The Echinides. These are the sea-urchins, properly so called, and 
the shells, when the animals are out of them, are called sea- 
eggs. The Echinides live in the sea. They lay eggs, and the 
roe, or imperfect eggs, occupy a large portion of the space 
within the shell when the animal is still alive. 
3. The Stellerides, or Asterias, are the star-fish. The mouth in these 
creatures is in the middle of the lower surface, and it has a 
membranous lip, capable of great dilation, but furnished with 
angular projections for capturing its prey. The skin is soft, but 
leathery, and it is covered on the back with spongeous tubercles, 
or scales. The rays are hollow beneath, and furnished with ten- 
tacula, by the aid of which the star-fish manages to crawl back- 
wards, forwards, or sideways, as the case may be, any of the 
rays serving as a leader. These animals are found on the sea- 
shore, forming large beds, which are washed over by the sea. 
The Crinoidea, or stone-lilies, of which such curious fossil spe- 
cimens have been found, are nearly allied to the star-fish. 
II. The Intestina, or Entozoa. The intestinal worms were divided into 
two kinds by Cuvier, viz. the Cavitaires, including the worms 
of children, and other cylindrical worms; and the Parenchyma- 
teux, or flat worms ; such as the fluke in sheep and the tape- 
worm in human beings. The Entozoa are now universally re- 
garded as belonging to the Articulated or Annulose division of 
the animal kingdom. 
III. AcalephcB, or Sea- Jellies. These creatures are of a soft and jelly- 
like substance, with a thin skin, and an unarmed mouth. The 
Medusides are very numerous, and produce that beautiful phos- 
phorescent light noticed by voyagers in the Australian seas. 
The most interesting of the Acalephes is the Portuguese man- 
of-war, or Physalia. 
IV. Polyps, or Anthozoa, according to Cuvier, were divided into 
three orders ; namely : 
1. Fleshy Polyps (Sea anemones) ; 
2. Gelatinous Polyps (Hydra) ; and 
3. Polyps with Polyparies, the latter including all the various com- 
pound zoophytes, with the Sponges. Of these the Flustrce, or 
Sea Mats, and numerous allied species, have since been recog- 
