12 MARVELS OF FISH LIFE 
fish, except the salmon family, most shore fishes, and a 
few deep-sea fishes, deposit these heavy, adherent eggs. 
As illustrations, I have shown the eggs of the roach, 
attached to submerged roots, and those of the perch, the 
latter adhering to each other, and forming long, glisten- 
ing ribbons, which are deposited on the roots and leaves 
of aquatic plants. 
Lastly, we have eggs lighter than water. These are 
free, and float near the surface, and are found only in 
the sea. From this type of egg are hatched almost all 
our marine food fishes. 
Floating eggs are very small, the largest being that 
of the plaice, which is about one-twelfth of an inch in 
diameter, and the smallest that of the dab, which is less 
than one-twenty-filth of an inch in diameter. Others, 
for example, those of the sole, the cod, and the turbot, 
are of intermediate sizes. 
Though, as stated, most of our food fishes hatch 
from floating eggs, herrings are an important excep- 
tion. Herring eggs are heavier than water, and are 
found attached to stones and shingle at the bottom 
of the sea. In estuaries of rivers flowing into the 
Baltic the eggs of these fish have actually been found 
attached to freshwater plants. 
Floating eggs are perfectly transparent before 
the embryo develops, and even a number of plaice eggs in 
a tumbler of sea-water are difficult to detect. This trans- 
parency is for protective purposes, for when floating in 
the sea they are invisible to their natural enemies. 
