346 



LAKES AND STREAMS 



common. Sticklebacks feed on insects, worms, the fry of other fish, and each other. 

 The three-spined species is remarkable for depositing its eggs in a nest made by 

 the male of fibrous materials, which he watches and defends until the fry are 

 hatched. 



The sticklebacks and the bullhead are the only British fishes that show any 

 sign of affection. " If the pike is the tyrant of the water," writes Mr. Pennell, 

 " the stickleback is certainly its knight-errant." The male stickleback commences 

 the work of nest-building by dragging water-weeds, algas, and other suitable 



materials to the 

 selected site, and 

 when this is ac- 

 complished, solidi- 

 fies the foundations 

 by strewing a few 

 mouthfuls of sand 

 upon them. The 

 next step is to 

 glue the materials 

 together, which 

 the little fish accomplishes by 

 drawing its body over the struc- 

 ture and depositing a mucus, 

 which is really a secretion from 

 the kidneys, and seems to harden 

 in the water. This is not the only 

 means taken for the stability of 

 the edifice, for after the mucus 

 has been applied, the fish may be 

 seen driving, by means of its 

 powerful fins, cm-rents of water 

 against the nest, evidently for the 

 purpose of finding if a weak 

 place exists. Should a grain of 

 sand or piece of weed be dis- 

 placed, it is immediately restored 

 to its position and firmly 

 cemented. Sometimes to try the strength of the structure still more vigorously 

 the stickleback rushes against it, and this not only once but repeatedly. The 

 whole building process generally occupies several days ; when the foundation is 

 once sure and complete, the next operation is to collect materials and build the walls 

 of the nest. The object of the fish is to build a barrel-shaped structure as smooth 

 as possible inside ; and for this purpose the process of selection and rejection 

 sometimes goes on for days and at other times four or five hours. The process of 

 cementing, after the structure is raised, is a long and laborious one, and it is not 

 finished until the whole edifice is perfectly sound and stable from an aquatic 

 point of view. Two apertures are constructed in the nest, one for ingress and 



«Wl 





KINE-SI'IXED STICKLEBACKS. 



