EFFECT OF CROWDING ON SURVIVAL 



183 



feet arms; i, tip gone; 2, end gone; 3, one- third arm gone; 4, one- 

 half arm gone; 5, two-thirds arm gone; 6, mere stump left. Indi- 

 viduals were removed from the bottles when they showed frag- 

 mented arms yielding on the foregoing scale a total value for the five 

 arms of a single starfish of 15-20, regardless of the distribution of 

 effects between the different arms. Table XIV gives the mean time 

 in days before each lot was discarded. The data at hand are faulty 



TABLE XIV 



Showing the Time in Days in Long Respiration Experiments before 



THE Different Lots Were Discontinued Because of Death 



or the Fragmentation of Arms 



* The Ophioderma in this column were isolated into liter flasks containing glass rods bent into various 

 shapes. 



in that, after respiration experiments were stopped, there were fre- 

 quently some individuals that had not yet reached the degree of 

 fragmentation necessary for removal. In some cases these were ob- 

 served, though under altered conditions, until autotomy had pro- 

 gressed past the arbitrary dead line; but in others this was not done, 

 and the last day of respiration tests was recorded for use in this 

 table. This procedure markedly favors the isolated individuals since 

 there were fewer of them so treated. The length of time the experi- 

 ment ran depended mainly on the temperature, since fragmentation 

 proceeds more rapidly at high temperatures. 



In every instance except one, the mean survival time was greater 

 for the bunched animals than for those isolated under similar condi- 

 tions and at the same time. In four of the six comparisons the dif- 



