DOCTRINE OF THE ACINETA-FOllxMS. 



103 



It can, therefore, no longer be doubted that from the 

 Acineta-embryo, after a prolonged motile stage, another 

 Acineta is formed. My observations do not, of course, show 

 that it is impossible that the motile Acineta-embryo should 

 be transformed into a Vorticella, and a VorticeUa-cyst into 

 an Acineta ; but the field of possibilities is very wide, every- 

 thing is possible if it only be founded on facts. I believe, 

 therefore, that it may justly be concluded that Stein's 

 Acineta-doctrine, as concerns Vorticella microstoma, Ehr., 

 must be regarded as hyvothetical, and not based upon 

 facts. 



