3,14 VICTOR K. S1IELFORD. 



and a large amount of experimentation would be necessary to 

 del ermine suitable tests for these animals and then all the 

 animals from both communities should be put through all the 

 tests new and old. A series of new tests must be added for each 

 new aquatic community and all the old tests must be so modified 

 as to secure good response from all the animals. Thus the labor 

 involved in comparing a number of communities is great. 



SAND-GRAVEL BOTTOM OR POOL COMMUNITY 



SPECIES 

 NOTROPIS 



HYBOPSIS 



AMBLOPLITES 



CALOPTERYX 



CAMPELOMA 



MACROMIA 



ANODONTOIDES 

 SPHAERIUM 



POSITIVE .WEAK LIGHT 



REACTIONS TOJ 



STRATA 

 OPEN WATER 



VEGETATION 



WHOLLY OR PARTIALLY 

 BURIED IN SUBSTRATUM 



MEDIUM LIGHT f^|f BURRuWING 

 SAND F~^ CURRENT 



FIG. 41. Showing suggestions as to the probable agreement and disagreement 

 of the reaction of the animals of the unsolved pool community on a basis of a total 

 of 300, introduced to show the striking differences between communities. 



VII. SUMMARY OF CONCLUSION. 



1. The animals of an animal community are in agreement in 

 the reaction to certain intensities of two or more factors. These 

 reactions may be used to designate them. Thus the rapids 

 community may be designated as litho-rheotactic meaning that 

 the animals are arranged with reference to current and stones of 

 considerable size. 



2. Animals living in the same or comparablesituations within the 

 community habitat are in agreement with respect to factors not 

 concerned in the general agreement and the animals of different 

 situations react differently to these additional factors. Similar 

 differences are the physiological basis for strata and consocies 

 though the small number of species makes the latter not easily 

 distinguishable here. 



