226 



ANIMAL AGGREGATIONS 



sea-water had been added to bring it to an equal initial resistivity. 

 These worms showed a mean survival of 18.38 hours longer in the 

 worm-conditioned water than in the controls. Each group of ex- 

 periments considered singly gave positive results, although some 

 individual pairs did not. Despite the variability in procedure used 

 in the different experiments, the combined results show a statistical 

 significance of 0.03 when considered as nine paired experiments. 

 These results are graphically summarized in Figure 17, which 

 shows two sets of histograms. That marked A gives in black the 



TABLE XXIV 



Showing the Effect of Procerodes-coKDiTiotiED Water upon Survival 

 OF Procerodes Isolated into Extremely Hypotonic Sea-Water 



Experiment 



Resistance in Ohms 



Conditioned Water 



Start 



Late 



Dilute Sea-Water 



Start 



Late 



Number 

 Tested 



Survival in Hours 



Con- 

 ditioned 

 Water 



Dilute 

 Sea- 

 Water 



Differ- 

 ence 



41-43 

 43-45 

 46-48 



49-51 

 52-54 

 71. . . 

 71a. . 

 73- ■ • 

 73a. . 



1 ,916 

 2, 100 



2,350 

 2,400 

 2,000 

 5,150 

 5,150 

 6,200 

 6, 200 



1,358 

 1,438 

 1,780 



1,930 

 1,320 

 3,550 

 3,550 

 4,700 

 4,700 



1,897 

 2,100 

 2,350 

 2,400 

 2,000 

 5,150 

 4,250 

 6,200 

 5,100 



1,445 

 1,480 

 1,760 

 1,888 



1,735 

 4,000 

 3,400 



4,500 

 4,000 



56 

 60 

 60 

 56 

 60 

 58 

 58 

 118 

 114 



88.16 



59 97 



58.1 



20.45 



10.05 



37.18 



37.18 



12 .06 



11.30 



13 



59-72 



22.94 



14 05 



9.29 



2.53 

 25.21 



23 95 

 4.31 

 342 



percentage of worms surviving at the indicated hourly intervals 

 when placed in tap-water with an initial resistivity of from 5,000 

 to 6,550 ohms. Just above, in the shaded blocks, is given the added 

 percentage of survival resulting from the presence of sufficient sea 

 salt to decrease the initial resistance to from 1,890 to 2,400 ohms. 

 The upper clear blocks give the added survival resulting from the 

 presence of water extract of Procerodes worms with the same initial 

 resistance as the hypotonic sea-water. 



Graph B shows similarly the survival in tap-water with an initial 

 resistivity of from 5,000 to 6,550 ohms, in hypotonic sea-water made 

 by adding dilute sea-water to pond or distilled water, bringing it to 

 a resistivity of from 5,150 to 6,550 ohms, and finally, at the top. 



