igoS.] JENNINGS— HEREDITY IN PROTOZOA. 493 



than different stages in the hfe cycle. The problem also can be 

 attacked in certain other ways, which will be described. 



The relation of diverse sizes to conjugation and the life cycle 

 was studied with special thoroughness in the case of a culture in 

 which there was an epidemic of conjugation January 29, 1908. This 

 culture was found in decaying vegetation from a small pond near 

 Baltimore; I called it culture M. Table LXI. (appendix) shows a 

 random sample of this culture, including both conjugants and non- 

 conjugants; of the 238 specimens in the table, 38 were conjugants, 

 200 non-con jugants. 



From this culture M a large number of pairs were isolated, for 

 various purposes, and allowed to multiply. Without going here into 

 the details of the experiments, on February 21 I had from this cul- 

 ture eight sets or lines, each descended from a single equal pair or 

 a single ex-conjugant ; these lines were designated in my notes L2, 

 Gi, Ai,A2, 1, C2, Fi and F2. (The designations are the same as those 

 given to the original pair or individual from which the lines came.) 

 In addition to these eight " pure lines," I had two cultures derived 

 each from eight pairs of conjugants of approximately the same size; 

 these were called Ki and K2. A final culture was derived from ten 

 small, nearly equal, non-con jugants from the same culture; it was 

 designated H. 



It is, of course, unfortunate that it is not possible to measure 

 accurately the original living individuals from which the different 

 lines are derived, but this will not alter in any way the results on 

 the problem in which we are at present interested. The essential 

 question is whether the lines derived from the different pairs or 

 individuals are identical or diverse in size. 



These various cultures were kept, so far as possible, in the same 

 nutritive fluid and under the same conditions. ]\Iarked differences 

 in size were apparent on examining the dift"erent sets with low power 

 of the microscope. On February 21 fifty individuals of each of 

 these eleven dift'erent sets were brought, with all the precautions 

 mentioned on page 489, into the same culture fluid, while at the same 

 time fifty specimens each of D and g of our earlier pure lines (see 

 page 491) were brought into the same fluid. These were all allowed 

 to multiply till February 26, when a random sample of 100 or more 



