88 LORANDE LOSS WOODRUFF. 



that this is the most accurate indication of the general meta- 

 boHc condition of the protoplasm of organisms which is 

 available. 



The work was started at the Thompson Biological Laboratory 

 of Williams College in the spring of 1907; was continued at the 

 Woods Holl Marine Biological Laboratory during the summer, 

 and is at present being carried on at the Sheffield Biological Labo- 

 ratory of Yale University. 



III. Details of Control Cultures. 



(a) Paramcchun aiirclia. 



The " wild " individual with which this culture {ParamcchtmV) 

 was started was isolated from an infusion in the Williams labo- 

 ratory on May i, 1907, and has been kept continually under ob- 

 servation since that time, and is at present (January 25, 1908) 

 in the 3 3 2d generation. The average rate of division of the 

 four lines (/— ^, I—h, I—c, I—d), again averaged for each five-day 

 period during the life of the culture up to present time, is plotted 

 by the familiar block method. By glancing at Figs, i and 2 

 (continuous line) it will be seen that the culture started off with 

 a division rate of just two divisions per day, and at the present 

 time, period 54, is averaging one and three quarters divisions 

 per day. 



I shall not attempt to analyze the division rate of the culture 

 in relation to the life cycle of Paraiiieciiivi at the present time, as 

 in the experiments under consideration it is of interest solely as 

 the " control." 



(^) StylonycJiia mytilns. 

 This culture (5"/j7(9;/jc///(^ I) was started with a "wild" indi- 

 vidual found in an infusion in the Yale laboratory on October 23, 

 1907, since which time it has been under daily observation and 

 has been subjected to the same method and treatment as the 

 Paraviecumi culture. It is at present (January 25, 1908) in the 

 165th generation. The rate of division is plotted in Fig. 3. 



