3o6 A HISTORY OF FISHES 



watchful father, who keeps them together in a compact mass 

 by circHng slowly around them. Many of the Cat-fishes 

 {Amiuridae) of North America excavate a rude nest in the mud, 

 a labour in which both parents share, and which may mean two 

 or three days of incessant work. Sometimes this nest is placed 

 in crevices in the river banks, beneath logs, stones, or even in 

 pails or other receptacles lying in the water. 



The Three-spined Stickleback (Gasterosteus aculeatus) constructs 

 a much more elaborate nest, and as the breeding habits of this 

 fish are of especial interest, they may be described in some 

 detail. The construction of the home is undertaken entirely 

 by the male, who sets about this duty before courtship is begun, 

 selecting a suitable site, such as one among the stems of aquatic 

 plants where the water flows regularly but not too swiftly, in 

 quiet shallows, or in rock-pools which are only reached by the 

 sea at high tides. He then collects pieces of the roots and stalks 

 of water plants, or any other vegetable rubbish, and cements 

 them together by means of threads of sticky substance secreted 

 by his own kidneys. Describing the building of a nest in 

 Vancouver Island, Mr. Lord writes: "During this operation 

 he swims against the work already done, splashes about, and 

 seems to test its durability and strength ; rubs himself against 

 the tiny kind of platform, scrapes the slimy mucus from his 

 sides, to mix with and act as mortar for his vegetable bricks. 

 Then he thrusts his nose into the sand at the bottom, and bring- 

 ing a mouthful, scatters it over the foundation; this is repeated 

 until enough has been thrown on to weight the slender fabric 

 down and to give it substance and stabiUty. Then more twists, 

 turns, and splashings to test the firm adherence of all the 

 materials that are intended to constitute the foundation of the 

 house that has yet to be erected on it. The nest or nursery, 

 when completed, is a hollow, somewhat rounded, barrel-shaped 

 structure, worked together much in the same way as the 

 platform fastened to the water plants; the whole firmly glued 

 together by the viscous secretion scraped from oflT the body. 

 The inside is made as smooth as possible by a kind of plastering 

 system; the little architect continually goes in, then, turning 

 round and round, works the mucus from his body on to the 

 inner sides of the nest, where it hardens like tough varnish." 

 Having finished the home, which often takes several days to 

 complete, he goes in search of a mate, and having selected one, 

 goes through an elaborate process of courtship, and finally 

 conducts her to the nest. He swims round her in evident 



