125 
Ninto Day. 
Fish Parasites. 
Nearly all animals harbour parasites. | When one 
animal lives attached to another, either clinging to the 
skin, or living inside the body, and feeding on the blood or 
juices of the animal to which it is attached, it is called a 
parasite, 
Thus the fish-louse found on the skin of the flounder 
is a parasite of this fish, and the flounder is said to be the 
host of the fish-louse. 
But the pea-crab which lives inside the shell of the 
mussel is not a parasite, for it does not live on the blood 
or juices of the mussel. It gets its food from the small 
animals and plants in the water which enters the shell of 
the mussel. 
The little white warts which are occasionally found 
on the skin of the flounder are also parasites, and not the 
egos of the fish as many fishermen imagine. 
Barnacles. Three different kinds of barnacles 
are frequently found by fishermen. 
1. The common barnacle, or “ scab,” which grows on 
the bottoms of boats during the spring. 
2. The ship barnacle. This does not grow in British 
Seas, but occasionally comes here attached to floating 
wreckage. 
3. The crab barnacle. This is a round soft animal 
which is often found attached to the under side of the tail 
of different kinds of crabs. It is not the spawn of the 
crab as many fishermen imagine; if it is opened its own 
spawn will be found inside the body. 
The common barnacle and the ship barnacle are not 
parasites, but the crab barnacle is. It is always a female 
which is parasitic on the crab, and the male barnacle 1s 
parasitic on the female, and lives attached to it. 
These three barnacles are very like each other when 
they are just hatched. 
