94 CORA D. REEVES 



C. Care of the fish 



13. The fish used in experiments with food 

 association were horned dace (Semo- 

 tilus atromaculatus, Mitchell) and Com- 

 mon Sunfish ( Eupomotis gibbosus Lin- 

 naeus). Individuals of these species as 

 well as of the blunt-nosed minnow, 

 Pimephales notatus, Rafinesque, the 

 Common Shiner, Notropis cornutus, 

 Mitchill, and the mud minnow, Umbra 

 limi, Kirtland, were used in experi- 

 ments on differential response. 



14. When not in the experiment aquarium, 

 the stock fish were kept in separate 

 aquaria. When needed for experiment, 

 they were transferred to the experi- 

 ment aquarium, where they lived often 

 for months together. During more 

 than two years these fish have shown 

 by feeding regularly, by lack of fear, 

 by continued growth, and by breeding 

 behavior that the conditions were nor- 

 mal for them. 



D. Experinients with food association 



I. Intensity jdiscrimination of white light 



15. Three full-grown individuals of the 

 horned dace were given an aggregate of 

 307 trials in an attempt to form a 

 food-association with the duller of 

 two white plates, the intensities of 

 which were as 1 :4. They failed to 

 discriminate these plates although they 

 learned to discriminate plates of greater 

 intensity difference, (p. 20.) 



16. Three sunfish, 4 cm. long, were tested 

 for intensity discrimination without 

 training by noting their behavior to- 

 ward two white plates. When the 



