I go 



ANIMAL AGGREGATIONS 



2 00 



180 



160 



140 



120 



100 



Fig. 1$. — Showing the total oxj^gen con- 

 sumption of isolated (solid line) and bunched 

 starfish (broken lines) in the different fifths 

 of the starvation experiments. The heavy 

 broken line gives the mean of the two 

 bunches shown by the lighter lines. Each 

 space on the ordinates represents i cc. of 

 oxygen. 



ing; hence, in the later stages 

 of the tests we are comparing 

 the mean rates of the most 

 hardy of the isolated individu- 

 als with that of a large bunched 

 group that has been subjected 

 to less rigid selection. 



When the differential autot- 

 omy is considered in connec- 

 tion with oxygen consumption, 

 it is found that the effect of 

 isolation is much more marked 

 than when only means of sur- 

 vivors are compared. These re- 

 lations are shown in Figure 15, 

 which gives the total oxygen 

 consumed, corrected for weight 

 of the different animal groups. 

 Again the initial value is that 

 which would have been con- 

 sumed had the initial rate held 

 for a period equaling the others 

 shown. It is added only for the 

 purpose of graphic comparison. 

 The preceding types of analysis 

 showed that after the initial 

 period the rate of oxygen con- 

 sumption remained approxi- 

 mately constant at their re- 

 spective levels for both bunched 

 and isolated individuals. On the 

 other hand, the complete data 

 show a decided falling-off in 

 oxygen consumption near the 

 end of the experiments, due to 

 the decrease in numbers of ani- 

 mals present. The effect of the 



