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 



(Fig. 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. 



