PARENTAL CARE AMONG FRESH-WATER FISHES. 



483 



The gTinnarehiis or huvo of the Giimbian natives manifests peculi- 

 arities in movement in accordance with its peculiarities of form and 

 structure. " It propels itself through the water, not by the action of 

 its paired fins, not by the motion of the tail or the undulatory motion 

 of the axis of the body, bnt entirely by the action of its dorsal fin." 

 ^AHien the fish starts forward, '• the motion is the result of a series 

 of waves passing backward along the dorsal fin. About five such 



Fig. 66. — GinnnarcJnis iiilotinoi. After Boulenner. 



waves are passing at a time. Suddenly the fish will proceed at the 

 same rate in the opposite direction, and now the motion is the result 

 of a series of waves passing forward along the dorsal fin. As the 

 g}^mnarchus swims rapidly backward in this way it may be seen to 

 guide itself through the grasses by using as a feeler this peculiar tail 

 which it possesses. Thus it appears to be quite immaterial to the 



MfUJ^ 



Hi{^. 



/ 



■%-k 







Fn;. 07. — Floating nest of Gymnarchus. After Budsett. 



fish which way it progresses, and it always appears to swim in com- 

 l)aratively straight lines." ^ 



The gynniarchus makes a large floating oblong nest, about -2 feet 

 long and 1 foot wide on the outside, iu'tlie dense grasses of a swamp 

 and in water o to 4 feet deej). In one, especially described by 

 Budgett. ''three sides of the nest projected from the water; the 



