RADIATES. 341 
derives its name from the lily-like form which some of its 
species present. Most of the species are extinct, but they 
are found in their fossil state abundantly in limestone 
and some other rocks. The other aberrant order is that 
in which are those animals that are called by sailors Sea 
Cucumbers, from their resemblance in form and in sur- 
face to the cucumber of our gardens. 
594. The second class of the Radiata is that of the 
Acalephs. These animals are called Sea Nettles and 
Stangfishes, from the stinging sensation which nearly all 
of them can inflict on being touched. They are also call- 
ed Jelly-fishes, from their great softness. Most of their 
bulk is merely water. Though one may weigh even 
many pounds when first taken from the water, when it 
has lost all its fluid parts it will weigh only as many 
grains. There are many species, some being no larger 
than the head of a pin, and some being of very consider- 
able size. 
595. One of the most common of these animals is the 
Medusa. This is often seen in great multitudes floating 
along near the shore in a calm, bright day. You see the 
shape and usual position of the animal in Fig. 268, B. 
Fig. 268. 
Its body is umbrella-shaped, with a fringe around its 
edge. It is by a waving motion of this umbrella that it 
moves along in the water. Its mouth is in the centre of 
the under surface, and from around it hang down four 
jeaf-like tentacula, which are both feelers and graspers 
