12 MARVELS OP 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-fifth 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. 



