INFUSORIA. 409 



a while develops a new nucleus, which passes through 

 the same stages as I have described, and bursts out, a 

 second Vorticella. 



But the cycle of changes may be quite different from 

 this. For sometimes the nucleus within the Acineta, in- 

 stead of forming a Vorticella, breaks itself up into a great 

 number of tiny clear bodies, resembling Monads, which 

 soon acquire independent motion, and glide rapidly about 

 the cell formed by the inclosed Vorticella-body as in a 

 little sea. But, by-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 upwards. The Acineta now collapses and disappears, 

 having done its office, while the embryos shoot hither 

 and thither in newly-acquired freedom. It is assumed, 

 on pretty good grounds, that these embryos soon become 

 fixed, develop stalks, which are at first not contractile, 

 and gradually grow into perfect Vorticellce, small at the 

 beginning, but capable of self-division, and of passing 

 into the Acineta stage, and gradually attaining the full 

 size of the race. 



Some forms of the same family, Vorticellada>, are 

 interesting as dwelling in beautiful crystalline houses, 

 of various shapes, always elegant. All these have been 

 ascertained to pass through the same or similar A cineta 

 stages. Cothumia imberbis is one of the prettiest of 

 these. The cell is of an elegant ampulla-like form, per- 

 fectly transparent and colourless, set on a stiff foot, or 

 short pedicle, which shows many transverse folds, like 

 those of leather. From the mouth of the vase projects 

 the animal, whose form may be distinctly traced through 

 the clear walls of the cell attached to its bottom, whence 

 it stretches upward when seeking prey, or to which it 

 shrinks when alarmed. 



In the former condition the body resembles a much 

 elongated Vorticella, with a similar circular orifice, set 



