PAIRING, COURTSHIP, AND PARENTAL CARE 305 



removed, leaving a layer of fine sand or gravel to which the 

 fertilised eggs adhere. The work is carried out entirely by the 

 male, who remains to guard the eggs until the young are hatched. 

 In many of the Cichlids [Cichlidae) the male constructs a similar 

 kind of nest, but both parents assist in the task of guarding the 

 eggs. Other fresh-water fishes make a nest by clearing a space 

 among aquatic vegetation. That of the African Osteoglossid 

 (Heterotis) is built in about two feet of water, is as much as 

 four feet across, and the walls, which are several inches thick, 

 are made up of the stems of grasses removed by the fish from 

 the centre, the floor being formed by the smooth, bare ground 

 of the swamp. One of the Mormyrids [Gymnarchus) constructs 

 a floating nest of large size, the walls projecting several inches 

 above the surface of the water at two sides and one end, the 

 opposite end, forming the entrance, being some six inches 

 below the water. One of the Mud-fishes {Protopterus) scoops 

 out a hole in the mud of a swamp, surrounded by long aquatic 

 weeds and grasses, the male alone being responsible for the 

 preparation of the home and for the subsequent care of the eggs. 

 Not only does he defend these assiduously against the depreda- 

 tions of hungry fishes, but, aerating the surrounding water by 

 lashing vigorously with his tail, he keeps the eggs well supplied 

 with the oxygen necessary for their development. The related 

 Lung-fish of South America (Lepidosiren) has a nest which takes 

 the form of a burrow excavated in the peaty soil of a swamp, 

 varying in length from three to five feet. The entrance is four 

 or five inches wide, and the burrow consists of a short vertical 

 part and a much longer horizontal portion, at the blind end 

 of which the eggs are deposited. The blood-red filaments 

 developed during the breeding season on the pelvic fins of the 

 male {cf. p. 301) probably have a respiratory function, enabling 

 the fish to remain in the burrow to guard the eggs without 

 coming to the surface to gulp air, and perhaps even serving to 

 aerate the stagnant water surrounding the eggs. The male 

 Bow-fin of North America {Amia) constructs a crude, circular 

 nest, usually placed at the swampy end of a lake where there 

 is an abundance of aquatic herbage, and when this is com- 

 pleted he is attended by one or more females, the fertilised eggs 

 adhering to the leaves and roots at the bottom of the hollow. 

 They are guarded henceforward by the male, who remains 

 constantly either on the nest itself or in a passage through the 

 reeds leading to it. After the young are hatched they are said 

 to leave the nest in a body, still under the protection of the 

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