76 
FISHES 
In the bull-head, they are found in the feelers, on the head, 
and even in the skin of the tail. The ear is under the skin, 
and there is no external opening. As water conducts sound 
vibrations more readily than air, no device for gathering 
sound waves is necessary. 
63. Reproduction. — The sexes of fish are distinct. At 
certain seasons many fish migrate upstream to lay their 
eggs (to “ spawn ”). Eggs are laid in large numbers by 
the females, and in the same locality sperm cells are dis¬ 
charged into the water by the males. The sperms unite 
with the eggs. The fertilized eggs hatch after thirty or 
forty days, or longer, depending on the kind of fish and 
the temperature of the water. The yolk of the eggs is 
attached to the young fishes for many days after they are 
able to swim, and supplies all the food they need during this 
time. (Figure 66.) 
The spawning habits of fish must be understood thor¬ 
oughly if they are to be raised artificially, as is done in the 
many fish hatcheries. Most states have scientific game 
laws which protect the fish during their egg-laying period 
when they are easily caught and when the destruction of 
even a few fish means the loss of thousands of eggs. 
