42 LIFE IN THE SEA [CH. 



act in the case of an egg-laying animal, or the birth of 

 the young in the case of a viviparous animal, almost 

 always occurs during the months of February to July 

 in northern seas. The majority of fishes, the cod, 

 plaice, flounder, whiting, haddock, and many others 

 spawn during the months of March and April. The 

 sole spawns during May and June, and the turbot, 

 brill, and gurnards about the same time, or a little 

 later in the year. The majority of invertebrate 

 animals also spawn during March, April and May. 

 The herring spawns somewhere in British seas 

 throughout the year, that is we have ' winter' and 

 'summer' herring. But even here the reproductive 

 act is a strictly periodic one for the various races of 

 herring spawning throughout the year are local ones, 

 each with its own reproductive phase. The act of 

 spawning lasts for a variable time : it is prolonged in 

 the case of the flat fishes, such as the plaice or sole, 

 where the eggs ripen in successive batches, but it 

 takes place quickly in the case of the round fishes 

 like the cod, where all the eggs come to maturity at 

 about the same time. It may be prolonged over a 

 month or two in the case of the skates and rays where 

 two large eggs are laid at a time. In the case of the 

 fishes which lay a great number of eggs that is in 

 the majority the numbers laid at first are few, but 

 they soon increase to a maximum and then quickly 

 decrease. Both the time of the maximum spawning 



