Fish as Nest-builders. 



acquired possessions ; for, should the site be a peculiarly 

 attractive one, other males will challenge his right to 

 it, and a series of combats will be fought over it 

 until the strongest and boldest male gains permanent 

 possession. Having successfully driven off all rival 

 claimants, the little Stickleback proceeds to dig founda- 

 tions and collect building materials. The foundations 

 take the form of a shallow depression in the sandy 

 soil, which the Stickleback makes by rolling his body 

 about thereon. Then he begins to collect delicate 

 vegetable fibres, selecting the smallest stems and root- 

 lets of various water weeds, placing them longitudinally 

 in the hollow already excavated for their reception, 

 and securing them in position by a secretion of mucus 

 from his skin. The floor of the nest completed, the 

 little builder proceeds with the erection of the walls, 

 using the same materials as employed for the floor, 

 leaving a small opening or door, finally crowning the 

 whole with a roof of similar material. 



By the time that the nest-building operations are com- 

 pleted, the little Stickleback has attained the full glory of 

 his spring colouring : he has donned his courting dress, 

 and is a most resplendent object, his breast and throat 

 mantled with scarlet hues, while his sides shine and flash 

 with metallic lustre. Off he starts to seek a suitable 

 bride. And here again we find his lordship somewhat 

 critical and hard to please. By no means does he pay 

 court to the first little lady Stickleback that may chance 

 to cross his path, and he may inspect and even carry 

 on a mild flirtation with several before he finds one to 

 fulfil his ideals. In this selection he is probably seek- 

 ing for one whose ova are ripe for spawning. The fair 



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