274 MOERIS M. WELLS 



Day ('87, p. 203) states that in a certain lake in the British 

 Isles, there is a race of tailless trout which some authors claim 

 can be traced as due to the action of deleterious matter in the 

 water. Day (loc, cit) also quotes J. Harvie-Brown as saying, 

 about 1876, ''that a contraction of the rays of the tail fins of the 

 trout in the river Carron occurred, and was believed to be due 

 to the continuous pollution of the water through the agency of 

 paper mills." Upon looking up the composition of the waste 

 from the paper mills (Griffin and Little '94, and Phelps '09) I 

 find that among other substances calcium is always present in 

 large quantities, both as the chloride and in other combinations. 

 Therefore the phenomenon reported by Day was likely due to 

 the presence of an excess of calcium in the water. 



Marsh ('07) has shown that the waste from paper mills is very 

 toxic to fishes. Calcium is not especially important, however, 

 as the toxicity of the waste is probably due to the excess of acidity 

 or alkalinity, and perhaps to other toxic substances. 



V. GENERAL DISCUSSION 



The experiments discussed in the preceding pages will be 

 considered very briefly in one or two phases of their general 

 bearing. From an ecological point of view they emphasize 

 once more the ability of fishes to recognize and react to environ- 

 mental factors in very small concentration. It should be pointed 

 out, however, that the reactions of fishes to salts in solution 

 are by no means so delicate as their reactions to acids and alka- 

 lies, i.e., to hydrogen and hydroxyl ions. As a matter of fact the 

 reaction to salts is complicated by the acid factor in many cases, 

 as, for instance, when the salt gives an acid solution, but more 

 especially in the numerous instances where there exists an an- 

 tagonism between the salt and the acid. Thus fishes may react 

 differently to a given salt concentration in water which is strongly 

 acid and water that is but faintly acid. The resistance experi- 

 ments show, also, that fishes can live in the presence of an acid 

 concentration which would ordinarily kill them, if the proper 

 concentration of the right salts is present. The work of Oster- 

 hout ('15) and others, as well as data presented iii this paper, 



