92 THE HAUNTS OF LIFE 
give them a big hold of the water. Some 
larval fishes, like those of the Angler, have 
long flexible ribbons floating out like decora- 
tions; and these probably help in flotation 
(ig. 7}. 
Some of the drifters have bodies large in 
size, but with so much sea-water in them that 
they cannot sink. They have almost the same 
specific gravity as the water. If we look into 
the sea from a boat we often see the common 
jelly-fish (Aurelia) opening and shutting its 
umbrella or disc a little below the surface. 
It looks quite large in the water, and for a 
time after it has been cast upon the shore 
by the tide. But a few hours later it has 
shrivelled up into a very papery heap indeed. 
Its body is made up of more than ninety per 
cent. of water, and when that has evaporated 
there is very little animal matter left. A great 
many drifting animals have this swollen, 
watery tissue. 
The presence of fat or oil serves the same 
purpose of lessening the body weight, and 
many of the smaller animals and some pelagic 
eggs have this character in common with the 
actively moving animals like the whales, 
porpoises, and many fishes. 
