Fish Migration 193 



in shore, hence many floating eggs laid 

 in the less saline water are provided with 

 oil globules to ensure their buoyancy. A 

 few like those of the angler are held 

 together in gelatinous masses covering 

 several square yards, whilst others like 

 those of the garfish are linked together 

 with a textile film. There is a general 

 tendency for currents at or near the sur- 

 face to move the floating eggs in a series 

 of ellipses. Whilst travelling the eggs 

 hatch, so that series of more or less con- 

 nected shoals of fry, varying much in 

 size and age, cover large tracks of the 

 ocean. This is known as " passive mi- 

 gration/' the young fish having to attain 

 some strength and resistive power in 

 order to direct their course. The well- 

 known shoal formation in which most 

 migrant fish travel has many advantages, 

 offering greater resistance to divergent 

 currents and ensuring more immunity 

 from enemies. 



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