SEVENTH ANNUAL MEETING 81 



so modified as to secure responses from all the animals. Thus 

 the labor involved in comparing a number of communities is 

 great. 



DESCRIPTION OF FIGURES 



Figure 8, showing the agreement and disagreement of the reactions of 

 the animals of the rapids community. Note agreement of reaction to bot- 

 tom and current and disagreement in two other reactions related to the 

 level at which the animals live. These results were obtained by placing the 

 animals under experimental conditions in which they had a choice between 

 different kinds of bottom, different strengths of light, and in which their 

 behavior in a water current was noted. In the case of water current the 

 percentage of animals headed up stream is given. When headed up stream 

 animals are said to be positive to current. In the case of the other 

 stimuli the percentage of animals in the kind of conditions available was 

 noted and the animals are said to be positive to the conditions in which 

 the greatest number are found. Thus we note that the darter (Etheos- 

 tom-a) was 80 per cent among the stones and is said to be positive to this 

 kind of situation. It will be noted that if the animals had been 100 per 

 cent positive to the various stimuli the entire 400 units should be occupied 

 in the diagram. This could be true only if there were no other factors 

 entering into the reactions of the animals. The common names of the 

 animals are as follows: Etheostoma, darter; Cambarus, crayfish; Gonio- 

 basis, snail; Hydropsyche, Caddis worm; Argia, damsel fly; Perla, stone 

 fly; Heptageninae, may fly; Psephenus, water penny. 



Fig. 9. Suggestions as to the probable agreement and disagreement 

 in the reactions of the animals of the unsolved pool community on the 

 basis of a total of 300 per cent. The common names of the animals are as 

 follows: Notropis, shiner; Hybopsis, river chub; Ambloplites, rock bass; 

 Calopteryx, damsel fly; Campeloma, snail; Macromia, dragon fly; Ano- 

 dontoides, mussel; Sphaerium, small bivalve. 



RECENT VIEWS CONCERNING ELECTRICAL CON- 

 DUCTANCE IN SOLUTIONS 



L. I. SHAW, NORTHWESTERN UNIVERSITY 



In 1801 Nicholson and Carlysle discovered that solutions 

 conduct, and ever since that time the question as to how they 

 conduct has been more or less of an open one. 



Let us first briefly consider two of the older theories of con- 

 ductance. The first one which we will consider is the theory 

 advanced by Grotthuss. According to this one, the substances 

 existed in the molecular state in the solution. On the passage 

 of the current the molecules first lined up, then split off and 

 then rearranged. This procedure was continued as long as the 

 current was passed. Clausius showed this to be incorrect, for 

 the reason that Ohm's Law holds for liquid as well as metallic 

 conductors, and if this is so, no electrical energy is used up in 

 breaking up the substance, but on the other hand, the ions must 

 already exist in the solution. The reason for a substance break- 



