OBSERVATIONS ON A FLAGELLATE OF CERCOMONAS. 257 



their being nuclei of spores destined to escape from the cyst 

 find ultimately to develop, with or without conjugation, into 

 the adult flagellate form. Though cysts have been constantly 

 kept under observation and every inducement possible to 

 encourage the emergence from the cyst has been tried, I have 

 never been fortunate enough to witness this process. That it 

 does occur is borne out by the experiment of adding dried 

 cysts to fresh medium, resulting in a culture of flagellates. 



In the stained preparation certain appearances are capable 

 of interpretation as a conjugation of the flagellates, and some 

 of the nuclear appearances as processes of maturation, but as 

 no undoubted conjugation was observed in the living flagel- 



Text-fig. 19. 







19. 



Cyst showing dark-staining granules surrounding the large 



central niiclens. 



iates I refrain from describing these. AVithout the control of 

 observation on the living* forms descriptions of conjugation 

 and the accompanying nuclear changes are of little value, 

 since the possibility of error in interpretation is very great. 

 For Copromonas major Berliner has described from stained 

 preparations such a process of conjugation, but without the 

 necessary controls it is always possible that abnormal or in- 

 volution forms have been mistaken for such stages. 



In rich cultures of the flagellates there is a very great 

 variation in size. Some individuals are comparatively large, 

 reaching a length of 15 ^t or more, excluding the flagella. 

 Others are very minute, being not more than 2-3 ju in longest 

 diameter. All intermediate sizes are to be met with in the 

 cultures. The encysted forms have a diameter of about 6/z or 



