210 



INTRODUCTION TO THE FISHES 



21,000 eggs. We must remember, however, that out of the large 

 number of eggs produced only a very limited number of young 

 reach maturity. Indeed, the production of a large number of 

 eggs usually implies an enormous destruction of eggs and young, 

 either by the action of enemies, by surrounding conditions becom- 

 ing unfavourable to their development, or from a scarcity of the 

 natural food supply. 



