48 CORA D. REEVES. 



be readily observed under wholly natural conditions ; the breed- 

 ing season is brief. Here if anywhere under field conditions it 

 should be possible to determine whether sexual selection occurs. 



I therefore attempted to observe continuously for as long a 

 time as possible the behavior of individual fish in order to learn 

 whether the more brilliant males succeed in spawning more fre- 

 quently than those less brilliant, and whether individual females 

 spawn more frequently with brilliant males than with those less 

 brilliant. Individuality in color pattern has made it possible to 

 thus follow and identify individual fish for several hours contin- 

 uously. I have further noted in a large number of cases the 

 colors of the pairing males in order to learn whether the more 

 brilliant males are successful in a larger proportion of cases than 

 the less brilliant males. 



From a number of records in my notebook I have selected 

 three of individual fish, that of a brilliant male (A), of a dull male 

 (B) and of a female (C). An extract from my field notes of May 

 1 8, 1906, gives an average picture of the movements of a large 

 male (A) that was under continuous observation for the latter half 

 of the afternoon of that day. He had his holding on a gravel 

 area just above a tiny rapid. The rapid was made by large stones 

 and debris which obstructed the course of the stream and formed 

 the lower margin of his area. Fig. 2 shows the breeding ground 

 of this fish. 



Fish A {Male). 



4:05 P. M. A female is in the area with A. There is spawn- 

 ing. 



4:10. Spawning is repeated ; a small male rushes in beside the 

 two fish. The female swims away with the small male while A 

 remains near the spot marked No. 1 in Fig. 2. 



4:13. A withdraws about a foot and begins to fight a male of 

 his own size ; both display their dorsal fins. 



4:15. A is back at No. 1. 



4:15^. He moves away less than a foot to where a female is 

 lying. Spawning again 8 inches from the first place (No. 2 in 

 Fig. 2). The female remains quiet while he drives off intruders. 



4:18. She goes away with a smaller fish that rushes in by her 

 side and pokes her. A remains near No. 2 and seems to be 

 feeding. 



