68 GEORGE ALFRED BAITSELL 



had a number of instances in which they hved and divided normal- 

 ly, thus showing conclusively that, even though the paramaecia 

 were in the physiological state in which conjugation could occur, 

 if they were separated before the supposedly essential factor of the 

 process took place, i. e., the exchange of nuclear material, they 

 could still live. Following the same method, split conjugation 

 was brought about in these experiments. The operation was 

 performed with animals that had been united only a few minutes, 

 and which were fused for only a short distance at the anterior end. 

 After the forcible separation, the resulting 'ex-conjugants' were 

 examined carefully and were found to be normal in appearance. 

 Three pairs of conjugants were separated and the resulting six 

 individuals were isolated. This was done about noon. By even- 

 ing of the same day it could be seen that they had changed very 

 greatly and appeared to be in a stage closely resembling that de- 

 scribed above as the first stage in the degeneration of the ex-con- 

 jugants. Three out of the six animals died that night and the re- 

 maining three during the next day. In these cases it appeared 

 that the mere contact of the gametes without any interchange of 

 nuclear material was sufficient to bring on a rapid degeneration and 

 death. 



VII. DISCUSSION AND CONCLUSIONS 



Although the conjugation which occurred in both of the cultures 

 kept on a beef medium in every instance resulted fatally, a careful 

 study of both the living and prepared material has failed to show 

 any reason why such should have been the case, but on the con- 

 trary such a study gives every evidence that the process which took 

 place was normally effected. 



The fact that conjugation is many times infertile and results in 

 the death of the ex-conjugants when the gametes have been kept in 

 laboratory cultures has been noted by a number of investigators. 

 Calkins (02a), for example, shows that of 80 ex-conjugants of Par- 

 amaecium caudatum from his laboratory cultures only five indi- 

 viduals, or 6 per cent were Hving at the end of thirty days; 37.5 

 per cent died without dividing and 60 per cent were dead within 



