THE SALMON FAMILY 53 
To return to the alevins in the gravel, at first the 
mortality amongst them is not great, but as soon as 
they begin to move about and get under the larger 
stones, their enemies play havoc amongst them. 
Sticklebacks and other small fish hunting in the 
gravel take their share, murderous-looking larve and 
caddis worms crawling into the darkest recesses 
still further diminish their numbers; and _ their 
constant enemy, the eel, is always on the look out 
for them. 
At five weeks old the alevins have acquired a more 
fish-like appearance, the fins are quite distinct and the 
adipose fin prominent, but notice that the tail fin is 
very unlike that of the adult trout. Though the alevins 
still derive some nourishment from the yolk sac for 
another week or two, they now begin to swim, and start 
feeding on minute infusoria. Next, the little fish tackle 
the young of tiny crustaceans, such as the cyclops and 
daphnia, or water-flea. At seven or eight weeks old the 
fins are separate and the yolk sacs have disappeared, and 
the alevins are now dignified by the name of “ fry.” 
Cyclops, daphnia, water-spiders, small beetles, larvee of 
water-flies, and young snails are now added to their 
dietary, and occasionally they are able to nip off the 
heads of their old enemies, the caddis worms, before 
these insects are able to withdraw into their protecting 
eases. If fortunate, the alevins come across a water- 
cress bed, where freshwater shrimps abound. The 
young of these crustaceans afford the best of food for 
