466 EVKNINGS AT THE MICEOSCOPE. 



regularly, pushing out its substance in tufts of threads, 

 and frequently protruding from one side a larger mass, 

 which becomes an adhering stalk. Thus it has become 

 an Acineta, such as we now behold. 



From this condition two widely different results 

 may proceed. In the one case, the encysted Yorti- 

 cella separates itself from the walls of the Acineta, con- 

 tracts into an oval body, furnished at one end with a 

 circle of vibratory cilia, by whose movements it rotates 

 vigorously in its prison, while the more obtuse end is 

 perforated by a mouth leading into an internal cavity. 

 In the interior of this active oval body there are seen 

 the band-like nucleus, and a cavity which has again 

 begun to contract and to expand at regular intervals. 

 It is, in fact, in every respect like a Vbrticella vase, 

 which has just freed itself from its stalk. Presently, 

 tlie perpetual ciliary action so far thins away the walls 

 of the Acineta that they burst at some point or other, 

 and the little Yorticella breaks out of prison, and com- 

 mences life afresh. The Acineta, meanwhile, soon 

 heals its wound, and after a while develops a new 

 nucleus, which passes through the same stages as I 

 have described, and bursts out a second Yorticella. 



But the cycle of changes may be quite different 

 from this. For sometimes the nucleus within the 

 Acineta, instead of forming a Yorticella, breaks itself 

 up into a great number of tiny clear bodies, resem- 

 bling Monads, which soon acquire independent mo- 

 tion, and glide rapidly about the cell formed by the 

 inclosed Yorticelloroo^j as in a little sea. But bv 

 and by, this body, together with the Acineta wall, 

 suddenly bursts, and the whole group of Monad-like 

 embryos are shot out, to the number of thirty or up- 



