64 GEORGE ALFRED BAITSELL 



this fact should be emphasized, the phenomenon of conjugation 

 which occurred in the two epidemics, judged by the study of the 

 hving material, gave every indication of being an entirely normal 

 process. 



In both the epidemics of conjugation, the syzygies were entirely 

 between closely related gametes. An endeavor was made, by mix- 

 ing animals from the stock slides of the conjugating cultures with 

 animals from the hay culture, to secure conjugation between gam- 

 etes which were not closely related and which had been under dif- 

 ferent environments. In both the epidemics this experiment was 

 tried a number of times but without success. The animals from 

 the hay culture were very evidently not in a state which would per- 

 mit of conjugation occurring. 



B. Prepared material 



No attempt was made in this work to secure sufficient perma- 

 nent stained preparations of the conjugating animals to permit 

 working out the cytological details of conjugation in this species. 

 The main object of the work was to study the physiological effects 

 of the phenomenon and permanent preparations were made prim- 

 arily to determine if a true process of conjugation had actually 

 taken place. Maupas mentions that he found this form to be a 

 very unfavorable one for the study of the cytology of conjugation 

 and no doubt any investigator will agree with this statement. 

 The nuclear changes which this form undergoes during the process 

 of conjugation cannot be worked out with surety without securing 

 an epidemic of conjugation in a mass culture and then making 

 use of the imbedding and sectioning method as used by Calkins 

 and Cull ('07) so successfully with Paramaecium. 



However, all the prepared material which could be secured un- 

 der the conditions of a pedigreed culture shows conclusively that a 

 true process of conjugation actually took plac^. A study of the 

 material reveals the fact that the niicronuclei are present in every 

 case and furthermore it appears that they are acting normally. 

 The appearance of the conjugating animals with the nuclear struc- 

 ture is clearly shown in figures 9 to 12. In figure 9 is shown a 



