FUNGUS OCCURRING IN PULVINARIA INNUMERABILIS. 317 



tion from that obtained among pathogenic parasitic microor- 

 ganisms. 1 



This indicates a nice physiological balance between the coccid 

 and symbiont and is another reason for considering this a case 

 of true mutualism. 



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1 In this connection it is interesting to note that we found antibodies devel- 

 oped abundantly in rabbits immunized against our cultures of the Pulvinaria 

 symbionts. 



