12 JACOB REIGHARD. 



downward so that they press against the sides of the tail and 

 sometimes against the anal of the female. The backs of the 

 males are arched and their dorsal fin-rays, spread like the ribs 

 of an extended fan, stretch the membrane between them (Figs. 



2,3)- 



The lateral surfaces of the anal and caudal and the sides behind 

 the dorsal, all of which are roughened by pearl organs (Fig. i) 

 are thus pressed vise-like against the female so that she is firmly 

 held (Figs. 2, 3). But the roughened caudals and anals of the 

 two males also press against each other where no part of the 

 female separates them. Thus the pearl organs aid males to keep 

 their positions with reference to the female as well as to each 

 other. 



When the fish have come into position there is a rapid vibration 

 of the whole bodies of all three together. This is wide and 

 vigorous behind the dorsal fin, while in the region of the head 

 it is a little more than a tremor. At this time the fish are often 

 in water so shallow that their backs are exposed. The powerful 

 movement of the tails of the three fish stirs up the gravel and a 

 cloud of sand is released and washed downstream. At this 

 time, in the aquarium, one may see milt spurt from the genital 

 openings of both males and cloud the water. No doubt the 

 eggs are extruded at the same instant and buried in the gravel, 

 but the water is made so turbid by sand and milt that I have not 

 seen the eggs laid. I have estimated the length of the spawning 

 act at a second and a half but have not actually timed it. It is 

 often repeated especially by the larger males. Large males are 

 often taken in which the front edge of the anal fin is raw and 

 \vorn by rubbing against the gravel. I have seen nothing of the 

 sort in females, but their anal fins are smaller than those of 

 males and are protected by them during the spawning act, while 

 the number of pairings of the average female can be but half 

 that of the average male. 



When a pairing act is completed the female moves on, usually 

 upstream, and presently pairs with other males on another part 

 of the breeding ground. Her eggs are thus scattered in small 

 lots over a considerable area, very likely over more than one rapid 

 and are commonly fertilized by many pairs of males. The two 



