BEHAVIOR AGREEMENT AMONG ANIMALS. 



303 



Comparing the rapids community with the pool community 

 which was studied only briefly and the resufts added here to 

 make the work on the rapids community clearer, we note that 

 the greatest activity was apparently in the 4-6 cm. per sec. 

 current (compare Figs. 19-23 and 27). None of the animals were 

 washed against the screen. All were active except Anodontoides 



STRAIGHT CURRENT 



le-20 CM. PER SEC. 



HYDROPSYCHE OR RAPIDS COMMUNITY SAND-GRAVEL BOTTOM OR POOL COMMUNITY 



p E R CENT 10 20 30 40 50 60 70 80 90 100 

 ETHEOSTOMA 



10 20 30 40 50 60 70 80 90 100 



CAMBARUS 

 GONIOBASIS 



PER CENT 10 20 30 40 50 60 70 n 90 100 



ETHEOSTOMA 

 CAMBARUS 

 GONIOBASIS 

 HYDROPSYCHE 



ARGIA 

 PERLA 



HEPTAGENINAE 

 PSEPHENUS. 



ORIENTATION POSITIVE 



27 



10 20 30 40 50 60 70 80 90 100 



NOTROPIS 

 HYBOPSIS 

 AMBLOPLITES 



CALOPTERYX 



CAMPELOMA 



MACROMIA 



ANODONTOIDES 



SPHAERIUM 



NOTROPIS 



HYBOPSIS 



AMBLOPLITES 



CALOPTERYX 



CAMPELOMA 



MACROMIA 



ANODONTOIDES 



SPHAERIUM 



INDEFINITE F?73 NO ACTIVITY I I 



FIG. 26-29. Showing reactions to 16-20 cm. current in per cent, positive, neg- 

 ative, indefinite, and inactive (26-27) and per cent, of active individuals positive, 

 negative, and indefinite (28-29). There was a large percentage of activity 

 among the rapids animals and a small one among the pool animals, due in the 

 case of the latter to inefficiency in the current. The rapids animals here show 

 the greatest per cent, of active individuals positive (compare with Figs. 18-25). 

 Temperature as for Figs. 18-20. 



and Splicerium, which moved in course of 24 hours but in the 

 direction in which they happened to be headed. The condition 

 indicated in the diagram is for a chance orientation allowing 

 1 6 deg. on either side of the direction of the current as respectively 

 positive and negative. 



In the 10-12 cm. current (Fig. 23) the amount of activity still 



