3O JACOB REIGHARD. 



surfaces of the males roughened by pearl organs. There is at 

 the same time more or less contact with one another of the 

 roughened surfaces of cooperating males and of those of the 

 female of the hogsucker with pairing males. Thus the pearl 

 organs aid the pairing fish to keep their positions with relation 

 to one another in the swift water during the vigorous vibrations 

 which characterize spawning. These vibrations are very pro- 

 nounced in the white sucker and red-horse but have not been 

 observed in the hogsucker. They continue in the white sucker 

 for about a second and a half and during that time the tails of the 

 fish agitate the bottom and the lighter bottom materials are 

 swept down stream by the current. 



When the pairing white suckers have separated, their eggs 

 are left buried in the bottom. This is inferred from the behavior 

 of the numerous minnows which congregate over the spot. 

 The similarity of spawning behavior indicates that the eggs of 

 the other species are buried in similar fashion. 



The females of the species studied deposit eggs in various parts 

 of the breeding ground and in doing so each pairs with many 

 males. It results from the breeding activities that the eggs of a 

 single female are widely scattered and are fertilized by many 



FIG. 8. Showing the distribution of pairings and their character over the 

 spawning area in the case of suckers in which two males pair with one female. 

 A, B, C, D, females; -w, x, y, z, males. 



males. It results further that the sperm of a single male fertilizes 

 the wide-scattered eggs of many females. The cooperation of at 

 least two males in pairing with a single female makes it impossible 

 to know the male* parentage of a given embryo. This same 

 cooperation makes it impossible that the eggs deposited in any 

 small, continuous bottom area should be fertilized by one male. 

 They are in fact not fertilized by one pair of males. The rela- 



