632 
RADIATA. 
Class IV. MSCOPHORA. 
This term is from tlie Greek diskos, a disc, and ^jhero, to bear, and alludes to the general form of 
the animals belonging to this class. They bear the popular names of 
Jelly-Fishes and Sea-Blubbers, from their gelatinous nature, and 
Sea-Nettles, from the stinging sensation they have the power of pro- 
ducing when touched ; the term Acale^ohce, wdiich has been generally 
applied to them, has this signification. They are exclusively natives 
of the ocean, which teems with them, from the intertropics to the 
polar circle. Among the strange and beautiful creatures which 
tenant the thronged and populous waters of the sea, they exhibit 
sometin:ies the most fantastic, sometimes the most elegant figures, 
adorned with colors of surpassing richness ; nor is their variation in 
size less striking than that of their forms. Some are so minute as to 
require the aid of a microscojDe, in their examination; others form 
large masses, which, as they float on the waves, cannot but attract 
attention. Many shine with phosphorescent brilliance ; as the 
vessel plows the briny water, or the oars of the boat throw up the 
spray, when dai'kness covers the face of the deep, they glitter like 
a shower of stars, and falling again, are lost in a sea of effulgence. 
Some appear in the depths like balls of glowing metal ; some move 
with an undulating course, appearing as they pass like a ribbon of 
flame ; others like diamonds gem the rocks or the fronds of sea- 
weed ; some float in shoals, displaying the lovely tints of the rain- 
bow ; while others, like orbs of silver, glitter as they float on the 
rolling current. They appear to be of a homogeneous and gelatinous 
consistence, but in reality are composed of filmy tissues, disposed in 
a cellular manner, and inclosing an abundance of sea-water, which^ 
when they are left dead on the beach, soon dries up, leaving only a 
little scum or gummy web behind. 
"In walking along the sea-beach," says Dallas, "as the tide is 
falling, the attention of the wanderer is often attracted by the number 
of singular gelatinous masses left on the sands. At first sight it 
would never be suspected that these are really living animals endowed with a structure of con- 
siderable complexity ; but a very little examination will soon show the observer that this is the 
case. If one of these lumps of jelly be put into a clear pool or basin of sea-water, parts, before 
confounded in a shapeless mass, immediately unfold themselves ; a circular, umbrella-like disc, 
surrounded by numerous short filamentous tentacles, appears to support the creature at the sur- 
face of the water ; and from the center of this, depend four long arms with 
membraneous fringed margins. This is the Medusa aurita, one of the com- 
monest species, and must have been often observed by those who frequent 
the sea-shore. In the water the creature swims along most gracefully by 
the contraction and dilatation of its transparent disc." 
All the animals of this class present a structure very similar to this. They 
all possess a disc of greater or less convexity, which is employed, in the 
manner already described, for the purposes of locomotion ; and in most of 
them the margin of this disc is furnished with tentacles or cirri. The disc, or umbrella^ consists 
of two membranes, of which the lower is called the suh-umbrella. In the center of this the mouth 
is situated, sometimes at the extremity of a peduncle of variable length, which contains the 
stomach, and in some cases also the ovaries. The mouth is most frequently furnished with ten- 
tacles. Some genera, although provided with a large peduncle or with tentacles, are said to have 
THE PELAGIA LABICUE. 
THE MEDUSA AUUITA. 
