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FISHES 



males, but others have observed only a single male to be pre- 

 sent. The latter account of the matter is easier to understand 

 since only a single male remains to tend the nest and eggs after 

 they are fertilised. The number of eggs in a nest vary from a 

 few hundreds to several thousands, but it is not known whether 

 they are always the product of a single female or of several. 

 A passage through the reeds provides access to the nest, and 

 the male remains on guard either in this passage or in the open 

 water of the nest itself; sometimes he remains for hours with- 

 out motion except the movements of the lateral fins and those 



Fig. 26. — Nest of American Bow-fin (Atnia calva) after Bashford Dean. 



of respiration, at other times he is more restless; he frequently 

 by vigorous respiration produces currents of water over the 

 eggs and thus supplies them with oxygen. The depth of water 

 in the nest varies from a few inches to three or four feet (Fig. 

 26). The eggs are hatched after eight or ten days and then the 

 male parent continues to take care of the larvae which remain 

 with him in a more or less compact swarm. For the first few 

 days the larvae remain inactive in the nest attached to fragments 

 at the bottom by their sucking discs. The young fish continue 

 to follow the male for several weeks and in one case Mr. Summer 

 in Minnesota observed a swarm of young which were three to four 



