Plate I. Electron micrographs of P. calk'msi, type 11, prepared to show the 



ciHum membrane. 



Reactive F. calkinsi, type II, were killed in 5% formalin, frozen in liquid air, and 

 lyophilized to the collodion membrane. The "blisters" in (1) and the expanded 

 membrane in (2) probably resulted from partial melting of the preparation during 

 lyophilization. 



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