THE GREAT DEEPS 117 
In rare cases it may be that organic matter 
in the water is simply absorbed by the animal’s 
body without any direct “feeding” at all, or it 
may be wafted into the mouth by tentacles and 
cilia, or it may simply sink into capacious open 
mouths, as in the case of abyssal sea-anemones. 
But many of the animals living on the ocean- 
floor are “‘ mud-eaters,” and as the rich “ ooze” 
passes through their food-canal the organic 
matter it contains is digested. The same thing 
happens in the case of the common earthworm 
as it eats its way through the soil, or in the 
case of the lobworms on the sandy beach. 
It may be asked how we know what deep- 
sea animals eat since we cannot of course 
actually see what takes place in the dark 
abysses. The answer is that the contents of 
the food-canal can be studied in animals 
dredged up, and also that we can carefully 
compare those that are brought up in the 
dredge with their near relatives living under 
different conditions, and try to make out what 
the differences between them may mean. 
Thus it is certain that many of the fishes at 
the bottom of the sea are voracious flesh-eaters. 
Some of them are of the usual wedge-shape, 
with long tails, but a great many are quite 
