n] RHYTHMICAL CHANGE IN THE SEA 43 



and the duration of the spawning act are variable 

 from year to year. The date of liberation of the eggs 

 depends on the temperature of the water until the 

 latter has attained a certain point it does not occur. 

 But it also depends on the temperature of the sea 

 during the month or two previous to the time of the 

 actual reproductive act, for the maturation of the 

 generative products proceeds slowly when the tem- 

 perature of the sea is low, and more quickly when it 

 is high. That is to say the temperature effect is partly 

 an integrative one. 



The growth phase begins almost immediately 

 after the completion of the spawning, for in some 

 way or other the parental habit compels the animal 

 almost entirely to neglect its own nutrition. Thus 

 the male lumpsucker, a shore-living fish, attends to 

 the mass of eggs laid by the female, the latter having 

 deserted them immediately on depositing them on 

 the sea-shore. It is necessary for the male parent to 

 i stand by ' the eggs and prevent them from being 

 devoured by other small fishes or invertebrates, 

 and to keep them supplied with a current of water 

 which he sets up by movements of his fins. During 

 all this time he refuses to feed (even if food is sup- 

 plied to him) while he and the mass of eggs are 

 being kept in an aquarium. But immediately after 

 the eggs have mostly hatched out he begins to 

 feed greedily. This is the case with nearly all fishes 



