66 



THE SOCIAL LIFE OF ANIMALS 



put into distilled water, a protective action which is 

 out of all proportion to its effect in increasing the 

 osmotic pressure of the water. We can demonstrate 

 that this is in fact the mechanism of such group 



1 Conditioned water 



Fig. 6. Procerodes die more rapidly if transferred to 

 pure fresh water than in dilute sea water, but live 

 longer if placed in fresh water in which other Procerodes 

 worms have died, even though the total amount of salt 

 is the same as in the dilute sea water. 



protection. For example, we can analyze the water 

 which worms have conditioned, find the amount of 

 calcium that has been added, and by adding that 

 amount directly get the same results that we do from 

 the conditioned water. 



This explanation is not yet complete— no scientific 

 explanation ever is— but we have demonstrated that 

 what was for a time a very mysterious group pro- 



