VORTICELLID^:. 165 



siderable increase in size, and at length break through the walls of the 

 cyst. After a time one of these projections of the internal substance 

 bursts at the apex ; and through the opening thus formed the gelatinous 

 contents of the cyst, the enclosed embryos, are suddenly shot out into 

 the water, there to become diffused, and give rise to a new generation. 

 From the name Acineta given by Ehrenberg to these, who described 

 them as a new genus, they are denominated Acineta-forms. 



But the final object of this singular metamorphosis still remains to 

 be described. The nucleus, which at the change of the encysted ani- 

 malcule into the Acineta-form was still distinctly observable, becomes 

 entirely and altogether converted into an active young Vorticella, ac- 

 quiring an ovate form, with a circlet of cilia round its narrower extre- 

 mity, and presenting at the opposite end a distinct mouth. Within 

 this young animal, whilst still inclosed in the body of its parent, we 

 see a distinct nucleus and the usual contractile space of the full grown 

 creature. When mature, the offspring tears its way through the mem- 

 branes inclosing the Acineta, which however immediately close again. 

 The latter continues protruding and retracting its filaments, and soon 

 produces in its interior a new nucleus, which in its turn becomes 

 metamorphosed into young Vorticella. 



The same faculty of inclosing themselves in a cyst is said to be 

 made use of by the Vorticella, as a means of self-preservation when the 

 water in which they have been residing dries up. When the animal is 

 thus encased, the mud of the bottom of the pool may be baked quite 

 hard in the sun without doing it the least injury; and in this state the 

 creatures are often taken up by the wind with the dust which it raises 

 from the surface of the parched ground and borne along to great dis- 

 tances, so as to cause their appearance in most unexpected localities 

 (they are frequently found in roof gutters), where the first shower of 

 rain calls them back to active life. These processes are repeated in 

 several of the allied genera with so little variation, as far as observa- 

 tions have hitherto shown, that it will be unnecessary to mention them 

 more particularly. 



Vorticella cyanthina, fig. 95, No. 7, has a fringe of cilia surrounding 

 the margin of its cup. A single animal is first seen, which increases 

 and then divides into two perfect animals, joined by a stem. 



Stentor, or Trumpet Animalcule, belongs to this family, fig. 100, 

 No. 4. Its body is of a trumpet-shape, and it adheres to its point of 

 attachment by a pointed extremity. They are of various colours white, 

 blue, yellow, red, and green. They swim in a parallel line to their sides, 

 sometimes tail first, rotating on their own axis. They attach them- 



