II 



EXPERIMENTS ON THE CAUSES OF 

 ENCYSTMENT AND EXCYSTATION 

 OF AMOEBA 



THE PHENOMENON OF " ENCYSTMENT " 



Introduction. It is well known that amoebae, 

 in common with many other protozoa, have the 

 property of assuming a resting stage under con- 

 ditions of environment which have been somewhat 

 vaguely described as "adverse to their welfare." 

 This process consists in the formation of a re- 

 sistant envelope to the delicate protoplasmic con- 

 tents of the organism, and is termed " encystment." 

 The species of amceba under consideration is no 

 exception to the rule, and the cysts formed in 

 this way are a prominent feature in all methods 

 of artificial cultivation. We believe that this 

 cyst formation should not be regarded as a phase 

 in the true life-cycle of the amceba, but should 

 be considered merely as a temporary condition, 

 which is assumed to protect the organism until 

 the surroundings are again suitable for its exist- 

 ence in the free living form. We are not aware 

 that the actual causes of this phenomenon have 

 hitherto been thoroughly investigated from a. 



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