46 CORA D. REEVES. 



truders. They may be called sham combats. Occasionally the 

 intruder resists. Then the two males range alongside each 

 other, depress their heads nearly to the bottom of the stream, and 

 with that peculiar trembling motion of the head already men- 

 tioned, and with synchronous movements of their caudal fins, 

 swim about here and there side by side or move side-wise across 

 the stream for short distances. The rivals when thus engaged 

 rarely swim forward from the holding yet I have once seen two 

 males swim forward for some ten feet, moving the caudal fins in 

 unison while keeping so close together as to seem to touch one 

 another. Professor Reighard tells me that he has observed a 

 similar form of behavior to be habitual with horned dace (Semo- 

 tilus atromacitlatus). 



5. Behavior of Supei'tiumerary Males toivard the Spazvning Pair. 



Young males frequently follow the female as she moves about 

 in the breeding area. They approach, as already described, and 

 tap her side ; they often move forward so that the tapping is near 

 her head. When thus disturbed the female swims off for a num- 

 ber of feet but does not often escape the small tormentors who 

 swim up beside her and continue their vigorous stimulation. They 

 are more agitated in their behavior than the larger males, especially 

 during the latter part of the season. As the large male guards 

 the female in the holding these young males often surround the 

 pair. They lie off at a distance of six to eight inches and make 

 frequent attempts to approach while the male in the center keeps 

 up a nearly continuous chase to drive them away. During the 

 spawning they often swim close to the side of the female moving 

 the gravel from near her as they wedge themselves in at her side. 

 When a number are present they may entirely cover the pairing 

 fish. During the spawning the small accessory males that are 

 in contact with the spawning pair move the body with the same 

 vibratory motion and thus appear to take part in the spawning. 

 They are not brilliantly colored. An examination of the milt 

 showed them to be nevertheless mature. The spermatazoa were 

 as active and when mounted in water their movements were as 

 long continued as in the case of large, brilliant fish. 



