EFFECT OF RADIUM ON CELL DIVISION 203 



Radium -placed f inch above eggs 



10 minutes 5 per cent retard 



15 minutes 10 per cent retard 



Radium placed 1\ inches above eggs 



10 minutes 5 per cent acceleration 



15 minutes Slight acceleration 



At a distance oi 2\ inches the radiations produced no decisive 

 effects. 



From these experiments it appears that during the prophases 

 the egg is more susceptible than during the preceding period. 

 An exposure which, during the first period produces an accelera- 

 tion, here produces a retard, indicating that the optimum amount 

 of radiation has been exceeded. 



3. Exposure made during the metaphase . Thirty-five to 

 fifty minutes after insemination. 



Radium placed f inch above eggs 



Le7igth of exposure Result 



5 minutes 5 per cent retard 



10 minutes 15 per cent retard 



(Longer exposures produced some abnormalities) 



Radium placed f inch above eggs 



5 minutes Slight retard 



10 minutes 10 per cent retard 



Radium placed 1\ inches above eggs 



5 minutes No change 



10 minutes 5 per cent acceleration 



15 minutes 10 per cent acceleration 



At 2| inches exposures up to 15 minutes produced no clear 

 cut effects. 



It is evident that the results noted here are of the same order 

 as those seen in the preceding experiment, but they are of greater 

 magnitude. It may be said therefore that eggs in this condition 

 are more susceptible than before. 



4. Exposures made during the telophases. Fifty to sixty- 

 five minutes after insemination. 



