No. 578] 



CYCLES AND RHYTHMS 



71 



Woodruff and Erdmann maintain that " under just 

 the proper conditions" conjugation will occur; this, of 

 course, can not be denied, but the fact that under the 

 same conditions some lines will conjugate while others 

 will not shows a physiological difference between them 

 which can not be gainsaid. I have no paternal jealousy 

 whatsoever in regard to the terms " conjugating lines" 

 and " non-conjugating lines," and am entirely willing to 

 accept in their place any terms which indicate the physio- 

 logical difference that I wished to express. I know of 

 no terms that express the conditions adequately. Substi- 

 tute for them, if more suitable, such expressions as 

 "always ready to conjugate" and "rarely ready to con- 

 jugate." Our observations on the 32 lines certainly jus- 

 tify the statement that some lines in regard to conjuga- 

 tion, were always ready, while others were rarely ready. 

 Woodruff and Erdmann have paid no attention to the 

 physiological conditions which the (perhaps unfortunate) 

 expressions "conjugating lines" and "non-conjugating 

 lines" were meant to express. It is true that after ten 

 months all but four of the so-called non-conjugating lines 

 each furnished a few pairs of conjugating individuals, 

 just as Woodruff's line did after six years, facts which 

 show that the terms "conjugating lines" and "non- 

 conjugating lines" as applied to races of Paramecium, if 

 used at all, should be used only in respect to relative in- 

 tensity of conjugating power. In this sense Woodruff's 

 race is a non-conjugating race. We have found, further- 

 more, that conjugating lines have a lower vitality as 

 measured by the division rate, and a much higher death 

 rate, than do non-conjugating lines, all but four of the 

 eight lines from the conjugating quadrant dying out 

 within three months as against four of the twenty-four 

 lines of the non-conjugating quadrants, while at the end 

 of twenty months only one conjugating line was alive and 

 sixteen non-conjugating lines, a mortality of 87.5 per cent, 

 for the former and 33.3 per cent, for the latter. In Para- 

 mecium it is conceivable that lines with a high conjugating 



