248 SOMETHING ABOUT JELLY-FISHES. 
until the movements have been actually witnessed. When 
contracted, these appendages occupy a space of exceeding 
minuteness, and when projected from the body seem to 
run out as a cable runs from a ship. We have sought in 
vain for any definite solution of the function of these 
threads, and are compelled to offer one derived from our 
own observations. Beside the locomotive power derived 
from the longitudinal zones of fringes, the body will be 
seen to oscillate to and fro, this motion being produced 
by the alternate contraction and relaxation of these 
threads, the resistance offered to the water by the sudden 
contraction of the expanded threads being sufficient to 
oscillate the body. The Jelly-fish in question, unlike 
most members of the class, swim with the mouth upward, 
and the appendages start from the pole opposite the 
mouth ; and since the mouth is unprovided with any or- 
gans whereby to grasp food, the mouth has the power of 
sweeping back and forth in the water by the oscillations 
of the body, affording greater chances of coming in con- 
tact with their food. It has the power of seizing little 
shrimp-like animals, and a singular sight it is to see this 
Jelly-fish, with its repast perfectly visible within its 
transparent body. 
There are two other forms of Jelly-fishes not uncom- 
mon in our waters, which have the zones of locomotive 
fringes, but have no trailing appendages, as in the species 
just described. One of these forms is called Bolina, and 
is spew larger than Pleurobrachia, being pear-shaped, 
and the larger jes divided into two lobes which surround 
the mouth. These lobes have the power of expanding 
and contracting, and the contour of the animal is mate- 
rially altered by their movements. They may sometimes 
be seen gaping wide, disclosing the mouth, and ready to 
