THE NESTING OF THE STICKLEBACK 19 



when the male fish has assumed his characteristic and brilliant colours 

 and the female is filled with roe, a pair should be introduced. 



It will be perhaps advisable to restrict the experiment to a single 

 couple,* as the male fish are very pugnacious. This is the outcome 

 of the care and attention which they lavish upon the nest and eggs. 

 When the young leave their home, which they do when the yolk sac 

 is absorbed, the parents should be removed from the aquarium or 

 they will probably devour their tiny offspring. The development of 

 the young stickleback should be compared with that of the trout 

 already studied. 



* This is the advice of Mr J. W. Gooch of Windsor, who has been most successful in 

 obtaining the nests of sticklebacks. 



