PHYSIOLOGICAL VARIATIONS IN PARAMECIUM 521 



9. SUMMARY 



1. Pure lines from eleven different series of Paramecium cau- 

 datum have been studied in cultures for periods of from five to 

 ten months. The pure lines were each derived from a single in- 

 dividual representing either the 4-cell stage or the 32-cell stage 

 of an ex-con jugant. Series J, E', and B are from the 32-cell 

 stages of different ex-conjugants, the J series being the oldest 

 and the most instructive. The pure lines were kept in small 

 vials (permanent cultures) under conditions of temperature and 

 feeding as nearly identical as possible. 



2. Relative vitality of the pure lines derived from the same 

 ex-con jugant is shown by a mortality in 'cleavage' up to the 

 32-cell stage, h mortality in the permanent cultures, and c the 

 daily division rates of representative individuals. 



3. a. JNIortality in the cleavage stages is high, only one series 

 (series J) giving the full set of 32 cells. In the E' series, four 

 died (i.e., one died in the 8-cell stage which should have given 

 four) ; in the B series four died (see p. 475). 



h. Mortality in the permanent cultures is also fairly high. 

 Nine died in the J series in ten months. Fifteen died in the B 

 series and ten in the E' series, in five months. 



c. The daily division rate for the 24 remaining lines of the J 

 series was kept for two different periods, one of thirty days, the 

 other of forty-two days, four months apart. Wide differences 

 were noted in the division rates of the pure lines during the first 

 period, minor differences during the second period. Possibly with 

 increasing age the entke population is approaching a common 

 type. 



4. Size variations are well-marked in the different lines. These 

 variations are as definite and as extensive as the variations in 

 progenies from different ex-conjugants. Variations, especially in 

 length, are also wide in vnsjiy of the same lines at different periods. 

 These periodic variations are more marked in non-conjugating 

 lines than in conjugating lines, the conjugating lines of quadrant 

 A in the J series giving to the entire quadrant a greater stabihty 

 than in any other quadi*ant (diagram 2) . 



