STICKLEBACKS. 59 



tank is clear enough to enable one to witness their 

 habits of life. They are, moreover, pugnacious little 

 fellows, and will attack other aquatic animals, or get 

 up fights among themselves, as if they had been 

 geographically limited to the " Emerald Isle." You 



Fig. 17. 



Three-spined Stickleback engaged in nest-building. 



may witness the male fishes carrying bits of weed, &c., 

 in their mouths, and building up a heap in some corner 

 in this manner. This work finished, their next task 

 is to induce some of their female companions to come 

 there and deposit their eggs. Whilst engaged in this 

 courtly office the males assume the most lovely pris- 

 matic hues, especially about the head and shoulders. 

 The females deposit their eggs or spawn, and then 

 leave it to their male companions to defend the spot 



