SEA-FISHERIES LABORATORY. 197 



seen inside its body. It is one of the things which cause 

 the phosphorescence, or " fox-fire," of the sea. 



Ceratium is another small animal which is some- 

 times extremely abundant in the sea. It forms a large 

 portion of the food of some small fishes. 



Fifth Day. 



C o p e p o d s. — These are the most abundant animals 

 in the sea. They are very small animals belonging to 

 the same class as the shrimp. Many young fishes live on 

 them, and they are the principal food of many full-grown 

 fishes like the herring and mackerel. 



A Copepod. — Magnified about 45 dia. 



The arrow worm is a little worm about an inch 

 long. It is nearly always found in the sea. It forms 

 part of the food of some fishes and it is said to eat fish 

 eggs. 



Other common animals found in the tow-nettings. 



Food of marine animal s. — Everything in 

 the sea lives on something smaller than itself. But this 

 cannot go on without coming to a stop, and in the long 



