152 MARVELS OF FISH LIFE 
to keep down the mussels. On a large oyster bed 
which had become smothered with mussels the experi- 
ment was made of importing star-fish. These soon 
destroyed the mussels, and when all the food on the 
bed was gone, they departed. 
Finally, crabs crack open the young oysters and 
devour the contents. From all this it will be realised 
that the oyster must go through many trials and 
tribulations before the final ordeal of appearing at 
table. 
There are many forms of life in the sea which, though 
smaller than the star-fish and oyster, well repay the 
trouble of collecting and observing, such as crab larve, 
various worms, and developing fishes. 
Minute creatures may be obtained in two ways: 
firstly, by pulling up seaweed, among which will be 
found quantities of interesting marine life—and this 
can be done by dragging from a boat a bar of metal 
armed with several hooks along the sea bottom; 
secondly, by towing a net through the water. 
““Mysis” is one of the interesting crustaceans 
collected in this manner. This crustacean is peculiar 
in having two auditory sacs on certain appendages of 
its body. The auditory sacs are well shown in the 
photograph and look like two little eyes. 
Constant reference has been made to the way in 
which one creature in the sea preys upon another, 
but everything must have a beginning, and for the 
ultimate food of fishes we must look to the microscopic 
