EFFECT OF THYROID ON DIVISION OF PARAMAECIUM 305 



Experiment VIII. October 21 to 25, 1913. 



Average Division Rate 



This experiment was performed after returning to New York 

 from Woods Hole and an interval at which observations were 

 made at irregular intervals (one to four days), periods 38-41 in- 

 clusive. At this time the Thyroid (V) still produced an increase 

 in division rate. 



Experiment IX. November 30 to December 19, 1913. 

 Average Division Rate 



This experiment was carried on 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 also in distortion, decreased size, more sluggish 

 movements and the appearance of monstrosities. Attempts 

 were made to save the race by changing the culture medium to beef 

 extract, increasing the amount of medium per individual, treat- 

 ing with K0HPO4, etc., but in spite of these efforts the last indi- 

 vidual died on December 20. At this period the thyroid (V) 

 did not produce any effect after the first two periods; in fact 

 the thyroid treated individuals succumbed more rapidly than the 

 control. The thymus treated individuals showed no significant 

 differences. 



