BEHAVIOR AGREEMENT AMONG ANIMALS. 295 



mechanical stimuli which lend themselves to experiment more 

 readily than many others. The pool community was studied in 

 a preliminary way to bring out the difference between different 

 communities. 



Over two hundred experiments were performed by Chas. W. 

 Finley and the writer working independently. It was originally 

 hoped that these might be used in this discussion but the difficulty 

 of adjusting conditions to which eight or more entirely different 

 animal species can respond, is great, and finally the use of the 

 first lot of experiments as a basis for comparison was decided 

 to be impracticable. This was due to faulty conditions which 

 gave bad results in the case of one or more species. However 

 these experiments gave a close knowledge of the behavior of each 

 species, so that when accurate methods were devised only 

 sufficient experiments to give typical results proved necessary. 

 These show experiments were conducted with much care and 

 are the only ones presented. 



II. MATERIAL. 



The material used were the species found habitually in rapids 

 and pools of Hickory Creek at New Lenox, 111. (Shelford '13)- 

 All the material used in the show experiments was collected in 

 late September, October, and November, 1913. It was kept 

 in as near natural conditions as possible in running lake Michigan 

 water with gases at saturation. Most of the material used had 

 been collected within three or four days but in a few cases material 

 one week old was used. Several of the species in question occur 

 outside of habitats of the type from which they were collected 

 for these experiments. These relations are given below. 



RAPIDS COMMUNITY. 



Etheostoma and Cambarus occur among and under stones. Goniobasi-t on stones, 

 Hydropsyche on and under stones. The remainder under stones. 



Species, Usual Habitat 



Rapids Occasionally in Rarely in 



Elheosloma coernelum Raf Pools of streams Lakes and large streams 



Cambarus inrilii. Hag Lakes Lake Mich. (Harris '03) 



Goniobasis Jivesfens Me Sandy hot lakes Veg. pool (Shelford '13) 



Hydropsyche sp Cn shells in moderate 



current Veg. in moderate current 



