MARINE PISCICULTURE 317 



2. It is a pure assumption that pelagic eggs 

 escape fertilisation in the sea. In all the records 

 of plankton examination I do not know of any 

 in which the presence of unfertilised pelagic fish 

 eggs has been observed. . An unfertilised pelagic 

 egg lives and floats for some days, and if such 

 did occur among the plankton, it is hardly likely 

 that they would have escaped record. 



3. We do know that an enormous destruction 

 of demersal fish eggs occurs in nature. Haddock, 

 for instance, have been taken with their stomachs 

 full of herring spawn. But we do not think 

 it necessary to cultivate herring. There are 

 instances on record of pelagic animals like 

 copepods, or the Chaetognathous worm, Sagitta, 

 doing the same with regard to pelagic eggs. 

 But these cases have not often been observed, 

 and we cannot say that the incidence of destruc- 

 tion in the life-history of a pelagic fish is greatest 

 during embryonic and larval development. It 

 is indeed possible that the greatest degree of 

 mortality may occur at a later stage. ^ 



4. The destruction which is assumed to take 

 place at the time of the total absorption of the 

 yolk-sac has not, so far, been avoided in the 

 hatchery. Indeed, it is from experience gained 

 in the hatchery (and from theoretical considera- 



1 This question might be resolved by the application of quantitative 

 plankton methods — by observing the relation between the numbers 

 of eggs at each different stage of development. 



