408 



TOXICITY AND SPECIKS. 



This is best determined with the use of low oxygen and carbon 

 dioxide and the data presented by Dr. Wells in the next article in 

 this volume shows such differences based largely on his experiments 

 along this line. In a general way the relative resistance of the dif- 

 ferent species to coal-tar products is similar to that given in his table. 

 According to our general experience with the orange-spotted sunfish 

 it should be rated at 12 in Dr. Wells' table. There are, however, some 

 outstanding exceptions. To the coal-tar products suckers are general- 

 ly about as resistant as the orange-spotted sunfish, and while in most 

 substances the green sunfish is more resistant than the orange-spotted, 

 it is less resistant to some of the phenolic compounds. 



3. FISH REACTIONS TO POLLUTING SUBSTANCES. 



The study of the behavior of fishes with reference to polluting 

 substances is a departure from the usual method of study of such re- 

 lations. The graphs on the charts show that fishes are as a rule indefi- 

 nite or positive to the substances which are not regularlv encountered 

 ill their environments. In other words they swim into the poisonous 

 solution without detecting it and turning back as they do in the case 

 of low oxygen and much carbon dioxide. They may go directly into 

 it without noting it, and after being for a brief time in the solution 

 they very generally avoid the pure water which is identical with that 

 in which they have been living for months even though the solution 

 chosen caused death. In some cases fishes at the beginning tend to 

 avoid the modified water, but soon, usually after a brief contact with 

 the solution, begin to turn back from the pure water, having very 

 cjuickly formed a preference or "habit" which keeps them in the 

 poisonous solution. Peculiarities of bcliazior occur in some cases with 

 reference to particular concentrations. 



The behavior results are of the greatest significance to the pollu- 

 tion cjuestion for since fishes are positive to fatal concentrations of 

 the vast majority of organic compounds introduced into streams by 

 gas-works, the tendency must be for them to enter rather than avoid 

 the portions of streams so contaminated, making the loss very much 

 greater than it would otherwise lie. The peculiarities of the reactions 

 to the various poisons is suggestive of a possibility of investigating 

 the physiological effects of habit-forming drugs. It is possible that 

 detailed study of these reactions might show why habit-forming drugs 

 produce a demand for more of the same drug, when several small 

 quantities have been taken. 



