SYNCHRONIZED GROWTH IN TETRAHYMENA CELLS 141 





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Figure 6. Synchronization by the modified procedure described for Figure 

 4. The growth medium was C. Mass growth has come to a standstill after 

 nine shocks ( 1 ) , at which time the cells are perhaps eight times larger than 

 the logarithmic cell (8). When released from the heat treatment after nine 

 or ten shocks (1, 2), all the cells split to logarithmic sizes within less than 

 18 or 17 hours (5, 6). When the release came after 12 shocks (3), many 

 cells failed to divide within 15 hours (7). Some cells adapted to and divided 

 during the cycling temperature after 12 shocks (3) or after 18 shocks (4). 



