INFUSORIA, 409 



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~bo&y 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 Vorticellw, 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 inter- 

 esting as dwelling in beautiful crystalline houses, of various 

 shapes, always elegant. All these have been ascertained 

 to pass through the same or similar Acineta stages. Co- 

 ihurnia imberbis is one of the prettiest of these. The cell 

 is of an elegant ampulla-like form, perfectly 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 

 round with cilia. Often the animal performs its ciliary 

 vibrations within the shelter of its house, not venturing to 



