RESISTANCE TO HYPOTONIC SEA-WATER 231 



whether it is an inherent property of the different heterotypically 

 conditioned solutions, is not yet apparent. At any'rate, the findings 

 to date are summarized in Figure 18, which gives the experience 

 from comparable experiments run simultaneously. The vertical axis 

 shows the percentage of worms surviving at any given time; the 

 horizontal axis gives the time elapsing since the beginning of the 

 experiment. One finds that there is a marked drop in the percentage 

 of survivals within the first 48 hours and that thereafter the curves 

 tend to flatten, reaching extinction in from 16 to 20 days. 



The mean survival for the whole group is not plotted on this 

 chart, but practically coincides with the graph for Proccrodes-condi- 

 tioned w^ater, except that it continues just above the base line until 

 after the 15-day mark. The graph for hypotonic sea-water having 

 the same initial resistivity runs below the lowest graph on the chart 

 at all points, except that at the 2- and 3-day periods it is very slightly 

 above this lowest graph. 



These results show clearly the lack of species specificity in the 

 protection of Procerodes against the lethal effect of hypotonic sea- 

 water; and remind one, in this respect at least, of the results ob- 

 tained by Allee and Schuett (1927) that protection from such toxic 

 substances as colloidal silver also lacks species specificity. The pro- 

 tection against colloidal silver appears in a large part to lack func- 

 tion specificity. Whether or not the present protective mechanism 

 also has other and general functions is not clear at the present time, 

 although on general grounds one would be inclined to think that 

 such would be the case. 



POSSIBLE FACTORS CONTRIBUTING TOWARD THE OBSERVED 

 SURVIVAL VALUE OF CONDITIONED SOLUTIONS 



The facts recorded are plain. The lethal effect of the fresh water 

 is clearly less for solutions that have been conditioned by the pres- 

 ence of living organisms, when compared with hypotonic sea-water 

 having equal initial resistivity. The exact source of this condition- 

 ing is not yet clear. In some of the Procerodes-conditioned media 

 the survival value is due to exudates from the living worms; in 

 others, where water extracts were prepared, the survival value may 



