2 JACOB REIGHARD. 



by others separated into the Catostomidse and Cyprinidae. To 

 accumulate the field notes and sketches on which the papers are 

 based has been the work of many seasons. If there were no bad 

 weather, no university duties, and no human interference with 

 breeding environment or breeding fish, such work might be 

 carried on with as little interruption as that of the laboratory; 

 but it would not progress as rapidly, for observations need to be 

 many times repeated. The behavior is often so complicated or 

 so rapid that it is only by analyzing it into its elements and 

 observing -each of these repeatedly that a degree of certainty is 

 possible. Such attitudes as these shown in Fig. 3 of this paper 

 may be correctly represented only after many observations on 

 the position of each fin and on every other detail. The observa- 

 tions upon which my descriptions are based have been very many 

 for each element of the behavior, often in the neighborhood of a 

 hundred, sometimes probably several hundred, or even thousand. 

 Although the work has been spread over a period of years no 

 one should suppose that the record is complete. I have studied 

 only the breeding behavior and that in but few fishes; I have not 

 the life history or the full natural history of any one. Of the 

 breeding behavior I shall try to give for each species a composite 

 picture taken from many fish through many seasons. This I 

 give in such detail as I have, because that seems necessary to 

 clearness. It further affords a better basis for the discussion of 

 theories to be considered in the final papers of the series. The 

 behavior that I describe may be easily seen in suitable places 

 and at the proper season. Yet few are likely to take the trouble. 

 This has seemed to me an added reason for fullness of treatment. 

 The suckers and minnows that I have studied, with the ex- 

 ception of the blunt-nosed minnow, Pimephales notatus (Rafin- 

 esque) breed .in running water. During the breeding season the 

 males of all the species studied have pearl organs, hard, tough, 

 white, usually conical elevations of the skin which consist of 

 cornified epidermal cells. They occur in many situations. 

 Some of them are so small as to be visible only under a lens; 

 others may be seen with the naked eye at a distance of ten or 

 twelve feet. They commonly make the surface of the breeding 

 males distinctly rough to the touch and are in that case referred 

 to as "effective" pearl organs. 



