FISHES 



247 



Life History. The breeding habits of fish vary so greatly that 

 it is difficult to make any general statements about their life history 

 to which there will not be many exceptions. 



The eggs vary in size from over an inch in skate, to the micro- 

 scopic offspring of the herring. Their number may vary from five 

 hundred in the trout to millions in cod, sturgeon, or flounder. 

 The eggs are fertilized after being laid, by means of the spermatic 

 liquid (milt) which the male sprays over them, sometimes stirring 

 the eggs and milt together so that more shall be fertilized. There 

 is little chance that all the eggs will be fertilized, since, as in the 



Stickleback Dogfish 



FIG. 89. Fish nests. From Pearse. 



plant, a sperm cell must reach each egg cell if it is to develop. 

 Hence the large number of eggs is partly to make up for the small 

 chance of fertilization. The eggs and young are prey to many 

 other fish and similar enemies, while man destroys the adults for 

 food, fertilizer, and fun. Out of enormous numbers of eggs, so 

 few survive, in some cases, that artificial fish culture has to be 

 utilized to prevent total destruction of certain species. In many 

 cases both the fertilization and the care of young are left to chance, 

 while in others, such as the bass, sunfish, trout, and catfish, a sort 

 of nest is made on the stream bottom, where the eggs are guarded 

 by the male, or may be covered with sand for protection. 



