PHYSIOLOGICAL VARIATIONS IN PARAMECIUM 473 



looked. After each test the organisms examined are thrown 

 away, the permanent cultures alone being maintained. Each 

 conjugation test therefore, involves organisms which have not 

 conjugated since the initial isolation of the ancestral cell. 



3. HISTORIES OF THE DIFFERENT SERIES STUDIED 



In addition to the J series started in July, ten additional series 

 have been studied for comparison; these, described under their 

 laboratory names, are as follows: 



1. The J series described above. 



2. The B series, started December 14, 1912, from a conju- 

 gating pair from a wild culture, 



3. The E' series started December 14 from another pair from 

 the same wild culture, 



4. The G series started on the same date from the same 

 culture, 



5. The H' series from the same, 



6. The L series, also from the same culture, 



7. The M series, 



8. The Q series, and 



9. The T' series, 



were all started on the same date from different pairs in the 

 same culture. 



10. The O series was started December 4, 1912, from a con- 

 jugating pair obtained from one of the conjugation tests of pure 

 line no. 8 of the J series and 



11. The P series was started December 3, 1912, from a con- 

 jugating pair from the same test. The history of these series 

 wall be described separately to avoid confusion. 



A. The J series 



It is not a simple matter to get 32 pure lines started from the 

 first four cells from an ex-conjugant. In the July set, no less 

 than 16 ex-con jugants were isolated and the progeny carried 

 through the preliminary divisions until some one or more indi- 

 viduals died, thus blocking the ejfperiments for that set, for it 



