LIFE HISTORY OF DIDINIUM 



237 



All efforts to recover the series from encystment failed ; not one 

 individual could be pursuaded to come out of its cyst, and the 

 race thus came to an end. 



Y Series: 2nd Cycle 



Chart D 

 GENERAL 



Encystment in ciliates has a three-fold purpose. First, for 

 protection against adverse conditions of the environment, which, 

 as Fermor has well observed, are usually so delicately adjusted 

 to the equilibrium of an organism that they baffle detection. 

 Such encystment is characterized by no internal reorganization 

 and the organism may be recovered in twenty-four hours or less 



