10:2 



OF FISH LIFE. 



in form, and always relatively small, sometimes 

 minute. Instances of an outer covering are, 

 however, numerous, but in such cases the cover- 

 ing is of a horny character, and is, furthermore, 

 often produced into frills, thread-like processes, 



FIG. 10. Sticklebacks and Nest. 



or other excrescences. The size of the egg 

 depends upon the number produced. This is 

 a quantity which may vary from several millions 

 to less than a dozen. When the number is 

 large the eggs, after they leave the parent, are 

 left more or less to chance ; when the number is 

 small they are often jealously guarded. How 

 and why this reduction of the eggs has come 



