AN AMICRONUCLEATE OXYTRICHA. II 149 



Cultures of these were begun the day following, when the 

 next fission occurred. Four lines in each were established, and 

 these continued to breed twins and single animals respectively 

 until the death of the series, which occurred March 3. Com- 

 ment on the similarity of the division rates is unnecessary. 



6. DISCUSSION 



In part I of this study it was shown that, while no true process 

 of syngamy was completed, there w^as reason to believe that the 

 organisms periodically made abortive attempts to conjugate and 

 that epidemics of cannibalism occurred. In the present paper it 

 has been shown that the formation of double annuals occurred 

 under precisely the same cultural conditions as those in which 

 pairing and cannibalism took place, i.e. this partial cytoplasmic 

 fusion, which has proved, contrary to all previous observations on 

 ciliates, to be permanent under suitable cultural conditions, 

 arose while the animals were in a physiological state strikingly 

 similar to that of true con jugants. Thus these three phenomena 

 are in this organism apparently related, and it is believed that all 

 three are but expressions of underlying physiological conditions 

 which are usually expressed by syngamy. 



The permanency of the union in the double animals is a nota- 

 ble feature, since in every series in which pedigrees were kept, 

 with the single exception of series 3 (p. 143), twin animals were 

 present until the series ended with the death of all the lines or 

 until the cultures were discarded. Further, it is noteworthy that 

 the 'miscible' condition of the protoplasm which made possible 

 the formation of a twin animal persisted as long as the animal 

 lived. That such was the case was demonstrated during the 

 separation of the two daughter cells in fission. At this time there 

 invariably occurred, in contrast to the final sudden separation 

 of the two similar cells of the normal single animal, the pulling 

 out of a relatively long thin cytoplasmic strand, enabling the 

 anterior cell to tow the posterior cell along for a considerable 

 period. In the case where a double animal separated by actual 

 pulling apart of the two components, a similar drawing out of a 

 cytoplasmic strand was observed, although in this case the con- 



