Chakt IV. 



Graph 35 shows the positive reaction of two minnows (Pimephales) to water 

 containing 2^^ cc. per liter of acetone. The fishes turned back repeatedly from the 

 pure water. 



Graph 36 shows the decidedly negative reaction of a minnow (Pimephales) to 

 water containing a fatal concentration of benzoic acid. 



Graph 37 shows the reaction of a green sunfish to water containing 0.5 cc. per 

 liter of phenol. The fish was markedly positive to the phenol during the first ten 

 minutes, when the activity increased, probably due to its irritating effects. The 

 greater part of the time was spent in the phenol however. 



Graph 38 shows the reaction of a full-grown rock bass to approximately 0.1 cc. 

 per liter of orthocresol, which would prove fatal to the fish in an hour or more. 

 When the fish entered the polluted water the first time it did not recognize it at all. 

 It gave no avoiding reaction. Later it moved toward the weaker solution and turned 

 back again into the stronger solution. After becoming partially intoxicated, it moved 

 into the pure water but returned to the fatal solution again and was completely over- 

 come there. 



Graph 39 shows the reaction of an orange-spotted sunfish to 0.3 cc. paracresol 

 per liter — about three times as much as is required to kill one of the fishes in one 

 hour. It is to be noted in particular that the fish after trying the pure water twice, 

 gradually avoided it more and more until it finally came to rest in the strongest 

 solution of paracresol. 



Graph 40 shows the reaction of two orange-spotted sunfishes to 0.12 cc. of 

 metacresol, sufficient to kill them in an hour. One fish was negative and the other 

 positive. The fish which happened to enter the polluted water at first became 

 intoxicated and remained positive thereafter. Fishes are often negative to meta- 

 cresol. 



Graph 41 shows the reaction of an adult rock bass to a saturated solution of 

 phenanthrene. Fishes are often indefinite to this substance. 



Graph 42 shows the negative reaction of an adult rock bass to a saturated solu- 

 tion of naphthalene. 



Graph 43 shows the positive reaction of an individual orange-spotted sunfish to 

 a saturated solution of naphthalene. Fishes are generally positive to this deadly 

 substance. 



Graph 44 shows the reaction of an adult rock bass to a mixture of pure water 

 3 parts and water saturated with xylene 1 part. The fish was decidedly positive and 

 was soon intoxicated. 



Graph 45 shows the reaction of a minnow (Notropis) to water containing ap- 

 proximately 0.08 cc. per liter of toluene. The fish is decidedly positive, though this 

 concentration would kill it in less than an hour. 



Graph 46 shows the reaction of two orange-spotted sunfishes to 0.04 cc. of ben- 

 zene per liter — suflficient to kill them in an hour. In this experiment the fishes 

 avoided the pure water and finally came to rest in the center. 



Graph 47 shows the reaction of a orange-spotted sunfish and a rock bass to a 

 Slightly weaker concentration of benzene than was used in the case of graph 46. In 

 this case the fishes both finally avoided the polluted water. 



