66 LIFE IN THE SEA [OH. 



feeble when compared with the distances to which 

 they may be carried by wind-drifts and currents. 

 They can have no control over the direction in which 

 they are being carried, and when the metamorphosis 

 occurs a process over which also the larva has no 

 control it must assume the habitat of the parent ; 

 and if it is a benthic form it must settle down on the 

 sea-bottom. If it is a littoral form a cockle or 

 barnacle for instance and if the eggs or larvae have 

 been transported into deep water, when the meta- 

 morphosis occurs the newly developed adult will 

 settle down to the sea-bottom and will be destroyed. 

 Or the larvae of a pelagic fish inhabiting deep water 

 may be carried into the brackish water at the mouth 

 of an estuary and will so be lost. It is easy to see 

 that very great numbers of planktonic larvae must 

 therefore fail to find their proper habitat at the time 

 when the transformation occurs, and this is one of 

 the reasons why most marine organisms produce 

 such large numbers of pelagic eggs the turbot, 

 for instance, may spawn as many as nine millions of 

 eggs each year ; even the relatively slowly repro- 

 ducing barnacle spawns about five to nine thousand 

 eggs. 



Yet the manner of distribution is not such a 

 hap-hazard process as it might appear to be, for 

 though the majority of larvae may fail to enter 

 adult life at the proper time or place, enough may be 



