140 BARBARA E. HOLMES 



caused a 12-hr delay in the onset of synthesis without aUerinp; the shape of the 

 DNA synthesis curve, and without altering the time relationship between the 

 peak of synthesis and the beginning of actual mitosis, in fact, there was no further 

 delay in mitosis. This means that DNA synthesis and mitosis were merely post- 

 poned for 12 hr and it does not mean that there was no damage to DNA, because 

 a large percentage of these cells coming into division showed chromosome 

 abnormalities (as detected by Professor Roller). 



