250 SOMETHING ABOUT JELLY-FISHES. 
members of this order are reproduced directly from 
eggs. 
We will now consider another order of Jelly-fishes 
called Discophore, or disk-like Jelly-fishes, since the 
form of many species present a disk-like appearance. 
Members of this order are very conspicuous in the water, 
owing to their large size, their opacity, and the distinct- 
ness of their egg-pouches. They have no zones of loco- 
motive fringes, but hanging below the disk and surround- 
ing the mouth are numerous appendages, and surrounding 
the border of the disk is seen a delicate fringe of threads 
interrupted at regular intervals by little dots called eyes. 
These Jelly-fishes swim in the water by successive ex- 
pansions and contractions of the disk, making a motion 
something like the motion made by the partial closing 
and opening of an umbrella. This motion is very leisurely 
performed, and the animal appears drifted by the currents 
and eddies with but little power to direct its course. 
Our most common species, the Aurelia (Plate 8, 
fig. 5), occurs abundantly in our bays, sometimes in 
vast multitudes. When full-grown they measure from 
twelve to fifteen inches in diameter. 
Another form, called Cyanea, often attains an immense 
size. Mr. A. Agassiz gives an account of one that meas- 
ured seven feet across the disk, and whose appendages 
stretched out to the length of one hundred and twelve 
feet ; their average size, however, is about one-third the 
dimensions just given. 
nettling sensation produced by certain Jelly-fishes, 
when brought in contact with the naked body, has long 
excited the attention of naturalists. The Cyanea is one 
of the mori fornidable in this respect, and Prof. Edward 
Forbes d ies as “the terror of ten- 
