138 ILLINOIS ACADEMY OF SCIENCE 



the male are used in this nest building according to Reig- 

 hard ('03, i). 531). As a rule one male works at a single 

 pit, but I have seen two digging at one and one working at 

 two pits. The fish frequently give chase to each other, 

 often with such heedlessness that they throw themselves 

 out on shore and get back to water with some delay and 

 considerable effort. They are sometimes found digging in 

 the pit or gravel pile made by the Horned Dace. Reighard 

 ('10, p. 1133) has also observed this, and he suspects that 

 they eat the eggs of the Dace. Stone-rollers feed extens- 

 ively and chiefly on the brown diatomaceous scum that 

 usually covers the gravel of breeding streams, and one 

 might easily mistake feeding for a breeding activity, but 

 when the digging is being done by the adult males only, 

 and Richardson '09, p. 110 and plate opp.), and when the 

 fish without these markings associated with them are not 

 taking part in the work, it is very likely that the operation 

 is a breeding one. More certainty is given to the conclu- 

 sion if the spawning act is observed. This takes place over 

 a pit by a male applying himself to the side of a female or 

 as observed in one case two males on either side of a 

 female. The contact is maintained but for an instant. The 

 pearl organs of the male enable him to maintain such con- 

 tact, according to Reighard ('03, p. 531). 



When the fish are working eggs are usually found among 

 the stones in or about the pit by taking up a handful of the 

 gravel and putting it in a shallow dish with a little water. 

 The eggs sink but move about readily when the water is 

 agitated. They are small, translucent spheres about a 

 1/20 inch in diameter and non-adhesive. To make the 

 identity of these more certain, I hatched some in my 

 laboratory and got fish eleven days old and about Vs inch 

 long that showed the intestinal peculiarities of Campos- 

 toma. Nest building in the Stone-roller appears to be a 

 process of bringing gravel to the surface to make a clean, 

 scum-free bed for the eggs. The advantages of nests of this 

 type are discussed by Reighard ('10, p. 1132). 



Pimephales notatus (Raflnesque), Blunt-nosed Minnow. 



This species breeds abundantly in our larger streams 

 and to some extent in the smaller ones, there being no evi- 

 dent general breeding migration in this region. The eggs 

 are placed in patches similar to those of the Johnny Darter 



