66 



Scientific Proceedings (52). 



tion, from the 27th of last July to the present. From the outset 

 marked differences in the size of the progeny of different lines 

 were noted; the statistical proof, however, is not yet ready for 

 presentation. A marked difference in division rate was also noted ; 

 for example, the daily division rate of representative individuals 

 of all the lines was carefully kept for a period of 30 days in October 

 and November. The average rate for individuals of the first 

 quadrant was 0.65 divisions per day; of the 2d, 0.91 per day; of 

 the 3d, 0.81, and of the 4th, 0.95 per day, a difference of from 

 fifteen to twenty per cent, between the rates of individuals from 

 the 1st quadrant and those of the other three. The weaker vitality 

 of progeny of the 1st quadrant is also shown by the extinction by 

 death of all the progeny of four lines of the eight, whereas only 

 one line died out from the progeny of quadrants 2 and 4, and none 

 from quadrant 3. (In quadrant 2, two lines failed to start by 

 reason of a pathological division in the third generation.) The 

 power to conjugate is correlated with these variations in vitality. 

 Conjugation tests (too complex to be described here) were started 

 in October and November, and many pairs were found in two 

 of the four remaining lines of the 1st quadrant, none in the others. 

 The December tests gave similar results; three of the four lines 

 of the first quadrant giving many pairs while none were found in 

 the other twenty lines. Again in January and February all four 

 lines of the first quadrant furnished many pairs, but not a single 

 pair was found in the other lines subjected to exactly the same 

 treatment. A specific example will show how extensive the ob- 

 servations were. In the January test, for example, not less than 

 150,000 Paramecium belonging to the non-conjugating lines passed 

 under my eyes, not a single conjugating pair being seen. Of the 

 four conjugating lines not less than 50,000 Paramecium were 

 observed, of which more than 2,000 pairs were in conjugation. 

 It is evident therefore that a very decided difference exists in the 

 total progeny of an ex-conjugant; some are potential germ-cells, 

 others apparently are not. These experiments may give a clue 

 to the divergent results obtained by Maupas, Woodruff and my- 

 self, which cannot be harmonized on the ground of abnormal 

 conditions or bacterial poisons in one case and not in another. 

 The divergence must be due to some more deeply lying cause in 



