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 larvae, 

 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 fife — 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 



