THE INFANCY OF FISHES 217 



mounts guard aver the eggs, but his vigil lasts only about 

 nine days. 



A very remarkable nest is built by the American " bow- 

 fin " (Amia calva), in the Eastern States of North America. 

 The female, it is to be noticed, may attain a length of 

 four feet and a weight of 30 lb., while the male is only 

 about two-thirds as large. In April and May the male 

 and female come up from the deep water to the reedy 

 shallows to spawn. Both sexes participate in the con- 

 struction of the nursery, which is formed by clearing 

 away the reeds over a large circular area — the fish actually 

 biting through the stems of all plants that cannot be 

 broken and pressed aside. Then a shallow depression is 

 formed at the bottom of the pool thus created, in which 

 the eggs are deposited. These develop with remarkable 

 rapidity, not more than eight days dividing the interval of 

 laying and hatching. This does not mean that the early 

 stages of development are passed within the body of the 

 parent, for the eggs are not fertilised till after extrusion. 

 The young are jealously guarded by the male, who keeps the 

 swarm together — often numbering as many as a thousand 

 individuals — by circling around and above them continually. 



The eel-like gymnarchus of the Nile builds a huge 

 floating nest of grasses, measuring some two feet long 

 and_ a foot broad. A part of the nest, curiously enough, 

 projects above the water. Within this about one thousand 

 eggs are laid, and as soon as they are safely deposited 

 the male mounts guard, defending them, and later the 

 young, with great ferocity. They certainly need pro- 

 tection, for, as we have already shown, they are for some 

 time anchored by an enormous weight of food yolk. 



Some of the frogs, it may be remembered, make nests 

 of foam : some species of fishes also construct cradles 



