PHYSIOLOGICAL VARIATIONS IN PARAMECIUM 479 



and P only two quadrants are represented, the other two dying 

 out before reaching the 32-cell stage. 



The histories of the 4-line series are interesting because they 

 indicate physiological differences in the first four cells derived from 

 an ex-conjugant. Twenty- two conjugating pairs were isolated 

 December 14, from a wild culture in an old hay infusion and the 

 44 ex-conjugants were followed in culture and the descendants 

 isolated until four pure lines from each were obtained or until 

 death of one of the early descendants made the series worthless 

 for these experiments when the series was discarded. Of these 

 44 individuals 15 died on the day following isolation without di- 

 \dding; 3 died on the second day without dividing; 5 were dis- 

 carded on the fifth day because of death of one or more quad- 

 rants; 5 were discarded on the sixth day because of death of all 

 the progeny of one quadrant; 1 was discarded on the seventh day 

 for the same reason; 2 on the twelfth day because of death of two ^ 

 quadrants; 3 gave four pure lines from the four quadrants, all of 

 which lived for three weeks when they were discarded because of 

 death of one or two quadrants; 4 were discarded for the same 

 reason at the end of one month, the remainder (6) continued to 

 live and form the basis of the experimental conjugation tests of 

 the 4-line series. In all of these cases of discard it must be borne 

 in mind that the entire race in each case had not died, only the 

 progeny of one or two of the original quadrants showing that 

 mortality is not evidence of hereditary weakness but of individ- 

 ual weakness. The remaining three or two quadrants were 

 healthy and normal and would undoubtedly have continued to 

 live. The extinction shows a relative weakness in some of the 

 progeny from an ex-conjugant while others are strong. In other 

 words, the same physiological variations that are found between 

 the progenies resulting from different ex-conjugants, are to be 

 found in the progeny from the same ex-conjugant. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 15, NO. 4 



