78 RHODA ERDMANN AND LORANDE L. WOODRUFF 



of a cell division in the climax, and this point must be definite!}' 

 settled for Paramaecium caudatum by further investigation. 



Thus, although we have presented sufficient data to establish 

 the occurrence of the reorganization process — endomixis — in 

 Paramaecium caudatum, we have found no new fundamental 

 facts to modify our brief theoretical suggestions as given in our 

 earlier study of Paramaecium aurelia. We believe the sug- 

 gestions — as there stated — must stand or fall on the basis of 

 further study of endomictic phenomena in other Protista. 



V. DISCUSSION AND CONCLUSIONS 



We proved in our previous paper that a periodic reorgani- 

 zation process, to which we gave the name endomixis, occurred 

 periodically throughout the seven years of the life of the main 

 culture of Paramaecium aurelia. We showed in subcultures, 

 from this main culture, in which conjugation was allowed to 

 occur that lines derived from exconjugants underwent endomixis 

 at the regular intervals. We thus proved that endomixis and 

 conjugation are phenomena common to the same race of Para- 

 maecium aurelia. 



We showed further that endomixis occurred in a race of Para- 

 maecium aurelia (culture B of our former pajDer) isolated in 

 Germany. On the basis of this we stated ('14, II, p. 494, and 

 '14, III, p. 474) : "Therefore, the data justify the conclusion that 

 this reorganization process is a normal phenomenon and proba- 

 bly occurs in all races of the species Paramaecium aurelia." 



But since Hertwig intimates that endomixis is probably a 

 peculiarity of Woodruff's main culture, we may cite further 

 evidence to substantiate our former conclusion. We have had 

 occasion, for certain experiments, to secure other races of Para- 

 maecium aurelia. One of these was obtained from material 

 sent to us by Prof. R. A. Budington of Oberlin, Ohio, and the 

 other from material sent by Dr. Florence Peebles from Bryn Mawr, 

 Pennsylvania. These two races, taken at random from material 

 collected at widely separated localities, immediately showed 

 endomixis at periods similar to those of the races p^^-eady studied. 



