VOKTICELLID^. 447 



The Vort'icella possess means of propagation which is 

 denied to other Infusoria, with the exception of a few^, 

 although we meet with the same in other forms of animal 

 life. The mode of reproduction referred to is called 

 gemmation; it consists in the production of a sort of 

 bud, which gradually acquires the form and structure 

 of the perfect animal. In the Vorticellce, these buds, 

 when mature, quit the parent stem after developing a 

 circlet of cilia at the lower extremity, and fix themselves 

 in a new habitation in exactly the same manner as those 

 individuals produced by the fissuration of the bell. 



At an earlier or later period of their existence, the 

 VorticellcB withdraw the discs surrounded by cilia which 

 forms the anterior portion of their bodies, and con- 

 tracting themselves into a ball, secrete a gelatinous cover- 

 ing, which gradually solidifies, and forms a sort of capsule, 

 within which the animal is completely inclosed. By this 

 process the little animal is said to become encysted; and 

 at this point of its history it is seen to be more compli- 

 cated. Sometimes its further progress commences by the 

 breaking up of the nucleus into a number of minute oval 

 discs, which swim about in the thin gelatinous mass mU 

 which the substance of a parent has become dissolved. 

 The body of the parent animal, inclosed within the cyst, 

 now becomes apparently divided into separate little sacs 

 or bags, some of which gradually acquire a considerable 

 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, 

 enclosed embryos, are suddenly shot out into the water, 

 there to become diffused, giving rise to new generations. 

 From the name Acineta given to them by Ehrenberg, who 

 described them as a new genus, they are denominated 

 xicineta-forms. 



But the final object of this singular metamorphosis 

 still remains to be described. The nucleus, which at the 

 change of the encysted animalcule into the Acineta-form 

 was still distinctly observable, becomes entirely and alto- 

 gether converted into an active young Vorticella, acquiring 

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



