414 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



in any of the other years during the intensive investiga- 

 tions. They also remained longer. Whiting eggs were 

 not observed before March 26th. They were present in 

 the plankton throughout April, and did not finally 

 disappear until May 24th. In 1910, they were noted for 

 the first time on March 11th, and continued in the area 

 till the end of April. The occurrence and duration of 

 the eggs in 1911 and 1912 were identical. Whiting eggs 

 were first observed on March 4th, and were one of the 

 constituents of the plankton till the end of April in each 

 of these two years. 



Gadus pollachius , Linn. — Pollack. 



Gadus virens, Linn. — Green Cod, Coal Fish. 



Gadus minutus, Linn. — Poor Cod. 



Gadus luscus, Will. — Bib. 

 The pelagic eggs of the pollack, green cod, poor cod 

 and bib are certainly represented in the plankton 

 collected in the area from the end of January to the end 

 of May. The difference in the size of the eggs of these 

 four species of Gadoids is so very small that it is quite 

 impossible to separate the four kinds when preserved. 

 In fact one cannot be quite certain even in differentiating 

 whiting eggs correctly from the eggs of the four species 

 mentioned above. It is well known that all the eggs 

 spawned by a female fish are not exactly the same size. 

 There may be a difference of at least one-tenth of a 

 millimetre between the largest and smallest eggs of a 

 single fish. This difference may be increased to three- 

 tenths of a millimetre when the eggs of a number of the 

 same species of fish are investigated. The range in size 

 of the eggs of one species of fish may easily overlap the 

 measurements of the extremes in the case of another 

 species. We find that the largest egg of the poor cod is 

 slightly larger than the smallest egg of the whiting. 



