596 



Lorande Loss Woodruff. 



rise took place for which there is no apparent cause, but this 

 recovery was not lasting and the rate fell somewhat during the 

 next period, while in the period following this all the infusorians 

 encysted, thus bringing the culture to an end at the two-hundredth 

 generation, and after being under observation for two hundred 

 and thirty-five days. 



Pleurotricha lanceolata, Culture A. 



2.0 



15 



1.0 



0.5 



0.0 



ijvirf 



100 



200 



Complete history of Pleurotricha lanceolata, Culture A, from start (November 10, 1902) to finish 

 (July 3, 1903). For method of plotting, see Diagram 11. 



^. Pleurotricha lanceolata, Culture B. 



A second culture of Pleurotricha lanceolata was begun Novem- 

 ber 25, 1902, with an individual found in some material in the 

 Columbia laboratory which had been recently collected at Van 

 Cortlandt Park, New York City. This culture was carried on by 

 the method used in all previous cultures for 480 days, and reached 

 during this time the 448th generation, when it was lost by an acci- 

 dent similar to that which terminated the Oxytricha.3~culture. 

 The culture-curve plotted in Diagram IV shows that throughout 

 the life of the culture a general average rate of nearly one division 

 per day was maintained. 



5. Gastrostyla steinii, Culture A. 



A culture of Gastrostyla steinii was started on May 28, 1904, 

 with a specimen which was captured in a hay-infusion in the 

 Williams College laboratory. For convenience I have desig- 



