540 



WALDO SHUMWAY 



treated did not show the decrease in division rate that is ob- 

 servable in the earher experiments, a decrease due to the increase 

 in death rate produced at the same time. 



TABLE 8 

 Race A. Experiment 8. Daily division rate averaged by five day periods 



Experiment A 8 carried on after return to New York from 

 Woods Hole and after an interval during which observations 

 were made at irregular intervals (one to four days) resi^lted in 

 the regular increase in division rate after thyroid feeding. 



TABLE 9 

 Race A. Experiment 9. Daily division rate averaged by five day periods 



Experiment A 9 was performed during the final depression 

 period which carried off the race. The individual cells at this 

 time gave evidence of their condition not only in lowered di- 

 vision rate, but in decreased size, more sluggish movements and 

 the appearance of monstrosities. Thyroid feeding produced no 

 effects after the first two periods and the thyroid treated line 

 succumbed more rapidly than the control. All attempts to save 

 the race by other food media, chemicals and increasing the 

 amount of culture media failed. 



These experiments showed that the thyroid fed individuals 

 divide more rapidly than those kept in hay infusion no matter 

 whether the race was at a high or low point in the life cycle. The 

 only exception obsei'ved was during the final depression period 

 which carried off the race. They also show that thyroid indi- 



