594 Lorande Loss Woodruff. 



allowed to run its natural course. A very slight falling of the 

 division-rate occurred in the next twenty days; but in the ten-day 

 period after that there was a more decided rise than had taken 

 place for a long while. This proved to be only temporary for 

 the Infusoria suddenly began to die off and within four days only 

 six specimens were left. Efforts to stimulate by artificial means 

 (K2HPO4, return to the usual hay-infusion, etc.) were unavailing, 

 and the last individual died on July 14, in the 860th generation — 

 626 days after the first isolation. 



2. Oxytricha fallax. Culture B. 



A second culture of Oxytricha fallax was started on December 

 10, 1902, with an individual found in a hay-infusion, made with 

 boiled water, in the Columbia laboratory. The method of pro- 

 cedure was the same as that already described for the A-culture. 

 The accompanying diagram shows the history of the fission-rate 

 of all four lines averaged together and this again averaged for each 

 ten-day period of the life of the culture. 



Culture B was continued for a period of 348 days during which 

 time it attained 429 generations. Its loss was due entirely to an 

 accident resulting in the drying up of the preparations. The general 

 rate of division for the first twenty-three periods averages about 

 one and one-half divisions per day, and compared with the curve 

 of Culture A, the curve of B is considerably more uniform. 

 From period 24 on (August), however, the rate shows a consider- 

 able falling off and it was averaging about one division in two 

 days — the lowest rate in its history — at the time that the culture 

 was lost. 



J. Pleurotricha lanceolota, Culture A. 



A culture of Pleurotricha lanceolata was started November 10, 

 1902, with an individual from an aquarium in the laboratory 

 of Columbia University which contained material collected during 

 the previous month at Fort Lee, New Jersey. The treatment of 

 the culture was the same as that already described for the 

 Oxytricha cultures. The general trend of the division-rate, as 

 shown by Diagram III, was steadily downward from the beginning 

 to the nineteenth period (May), when the low rate of one division in 

 eight days was reached. During the next three periods a marked 



