488 



PARENTAL CARE AMONG FRESH-WATER FISHES. 



fectly clean and clear, so that I could see with my water telescope the 

 eggs nearly covering the bottom of the nest. When all the eggs are 

 laid the firii leaves the nest by a hole at one side." 



The nest appears to be used " for at most four or five days." The 

 eggs, it was thought, were hatched in about two days. The larva? had 

 lonir external blood-red gill filaments. 





^■'^M. /// 





Fig. 73.— Nest of the Heterotis. After Budgett. 



As soon as they are released they strike out from the bottom, and, 

 the day after hatching, "may be seen continually parsing up and 

 down." The next day '' they cease to pass up and down, and converg- 

 ing to a swarm about one foot in diameter, form a deep continuous 

 circle remarkable for its regularity and persistence. The swarm occu- 

 pies the exact center of the little lagoon. The young fry, which by 

 now have lost the long external gill filaments, are seen to be steadily 



Pig. 74. — Heterotis nilotirus, larva, a clay after hatehinu 



After Budget. 



careering round and round, ever in the same direction, for at least a 

 day. About the fourth day the swarm becomes less persistent and 

 regular, the larva^ swimming first to one side of the nest and then to 

 the other, until about the fifth day they leave the nest by the exit for a 

 few trial trips, attended hy the parent, and finally leave it altogether, 

 swimming hither and thither in a dense swarm, from which the par- 



