Chart II. 



The relations of tank length to time scale is the same as in Chart I. In the 

 case of this and all the charts which follow, the polluting substaneie was introduced 

 into the right hand end of the gi-adient tank and is accordingly shown, at the right 

 side of the graphs. The vertical broken lines are intended to indicate the location 

 of thirds of the tank length. The solid black area at the right between the two 

 lines at the head of each graph is intended to show the part of the tank in which 

 the polluted water is full strength and the narrowing of this black area from right 

 to left in the middle third is intended to indicate the region of principal gradient. 

 The unpolluted water contained about 5 cc. CO, per liter. X indicates that the fish 

 became intoxicated; the arrow that it Avas driven. 



Graph S shows the positive reaction of an orange-spotted sunfish to 1 part of 

 weak waste to 25 parts of water. The fishes avoided the normal water and remained 

 most of the time ill the high concentration and gradient. 



Graph 9 shows the reaction of the golden shiner to waste, 1 part in 100 of 

 water, which killed the standard fish in a little more than one hour. In this case 

 the fish avoided the unpolluted water and did not enter it at all until driven as indi- 

 cated by the arrow. 



Graph 10 shows the reaction of an orange-spotted sunfish to the same solution 

 as was used in the case of graph 8. In this case the fish was negative, showing that 

 there is some variation in the reaction. 



Graph 11 shows the reaction of a minnow (Pimephales) , indicated by the broken 

 line. The fish was negative for a time but became intoxicated after a little more 

 than two minutes and then remained positive after being driven into the strongest 

 solution. 



Graph 12 shows the reaction of an orange-spotted sunfish to illuminating gas. 

 There was little activity and one fish remained in the clear water while the other 

 remained in the polluted water during the period of observation. The amount of 

 illuminating gas was not determined ; much more was forced into the water Ihan 

 would go into solution in the pipe of the lower cooler (Fig. 1, preceding Chart I). 



Graph 13 shows the reaction of a large-mouthed black bass to illuminating gas 

 under the same conditions as in graph 12. The fish was driven into the stronger 

 solution of gas and reacted positively thereafter. 



Graph 14 shows the reaction of the golden shiner to a solution of ammonia which 

 would prove fatal in a short time. The fish on the whole remained most of the 

 time in the part of the tank containing a somewhat diluted solution but gave no 

 avoiding reactions. 



Graph 15 shows the positive reaction of a minnow (Xotropis) to ammonia 

 solution under the same conditions as graph 14. In this case the fish was clearly 

 positive. 



Graph 16 shows the positive reaction of two individuals of Notropis to a solution 

 of approximately one gram per liter of NH. (CO), which kills such fishes in less 

 than an hour. 



Graph 17 shows a decidedly positive reaction of a rock bass to approximately 1 

 gram per liter of ammonium chloride. The experiment continued for 10 minutes after 

 the portion shown without change of result. 



Graph 18 shows the reaction of a rock bass to 0.7 gram of ammonium sulphate 

 I>er liter. The fish rested in the polluted water throughout the greater part of the 

 time and turned back when a decreased concentration was encountered. 



Graph 19 shows the reaction of a minnow (PiinepJiales) to approximately 0.25 

 gram of ammonium sulphocyanate (sulphocyanide) per liter. The fish moved back 

 and forth actively and turned back regularly from a pure water. 



Graph 20 shows the reaction of a full-grown rock bass to the same concentration 

 as in Graph 19. The fish was driven into the pure water at the end of seven minutes 

 but soon returned to the polluted portion. 



