10 



JACOB REIGHARD. 



conditions. As the males approach the resting female she 

 hurries forward as though to escape, but presently stops with 

 her belly. on the bottom. As the males again approach she hur- 

 ries forward a second time, but soon stops as before. .Thus she 

 appears to be driven here and there over the spawning ground, 

 too "coy" to allow the males near her. After a varying number 

 of apparent efforts to escape her "coyness" vanishes and she 

 rests quietly on the bottom and permits the males to come near. 

 In what follows I describe the spawning behavior as I saw it very 

 many times from the bridge or from the banks of Mill Creek. 

 Details were observed several times in the aquarium (Fig. 4). 



When a male comes within a few inches of the waiting female 

 he is often seen to stop, spread his pectorals, erect his dorsal and 

 protrude his jaws (Fig. 4, second fish from bottom). Then, for 

 perhaps a second, his head trembles with a slight, rapid vibration 

 from side to side. The movement is not unlike the tremor of 

 a palsied hand. It is like the tremor that one may produce in- 

 his own head by strong continuous contraction of the muscles of 

 the neck. This tremor may be seen not only when a male 

 approaches a female, but often when he approaches another 

 male on the spawning ground. I have never seen it in a female. 



FIG. 2. A female of Catostomus commersonii engaged in pairing, with a male 

 on each side of her. The body and tail of one male are shaded. The pearl organs 

 are shown on the anal and caudal of the nearer male, but not elsewhere. The 

 figure represents the pairing act near its end with the head of the female well above 

 the bottom, which is represented by the irregular horizontal line. Drawn with the 

 help of a photograph (see Fig. 4). 



It is probably nothing more than a beginning of the tremor of 

 the whole body which accompanies spawning. It necessarily 

 produces a vibration in the water which may be of such a rate 

 as to stimulate other fish through the skin, ear or lateral line 



