THE THEORY OF TITTLEBATS. 



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As soon as the pairing-season sets in, the first care of the male 

 stickleback is to provide a nest for his wife and children. For the 

 stickleback is just as much a nest-builder as any bird ; only, he does 

 all the work himself, instead of being aided, as birds usually are, in 



Sticklebacks and their Nests (Gasterosteus aculeatus). 



the task of nidification, by his attentive partner. He begins by busily 

 collecting a quantity of delicate fibrous material, the tissues of water- 

 weeds or of macerated land-plants, which he mats with his mouth into 

 an irregular circular mass, somewhat depressed, and about an inch and 

 a quarter in diameter. Then he covers the top with similar materials, 

 and leaves in the center of one side a large, round aperture to act as a 



