EFFECT OF CROWDING ON SURVIVAL 



193 



present after the glass rods were added. The table gives a compari- 

 son of the initial respiration of 24 Ophioderma isolated into flasks 

 containing glass rods, with that of 48 isolated into plain flasks, and 

 with 96 divided among the accompanying bunches. 



The Ophioderma associated with the clean glass rods consumed 

 more oxygen per individual in 5 out of 6 cases than did their asso- 

 ciated bunches. The mean dift'erence of 70 cu. mm. is beyond the 

 statistical border of significance, since there are 85 chances in a 

 1,000 in this case and 112 in the next, that random sampling would 

 give so great a deviation from the mean. On the other hand, the 



TABLE XVI 



Showing Final Mean Relations in Oxygen Consumption of Ophioderma 



Separated under the Conditions Shown for the 



Heading for Table XV 



(The Results Are in Cu. Cm. of Oxygen Calculated to 

 Equal \\^eight for Each Series) 



individuals associated with the glass rods consumed less oxygen than 

 the accompanying animals isolated into plain flasks, in 4 out of the 

 6 cases, with a mean difference of 107 cu. mm. Thus the initial 

 effect of the presence of the heap of glass rods with the isolated in- 

 dividuals was to produce a rate of oxygen consumption intermedi- 

 ate between that of the bunched and the other isolated individuals. 

 The position of the mean, nearer to that given by the bunched indi- 

 viduals than to those isolated in plain flasks, while suggestive, is not 

 significant statistically. 



The results in the two total respiration experiments which con- 

 tained this feature are given in Table XVI. Here the presence of the 

 glass rods was accompanied by an even greater total oxygen con- 

 sumption than that of the bunched individuals and, as was shown 

 in Table XIV, the autotomy effects are more closely related to those 

 of the bunched than to those of the other isolated animals. 



