VorticelUna.'] iNFUsoniAt ANiMALCULEg. 519 



Family.— VOETICELLIJfA. 



These polygastric animalcules are provided with an alimentary 

 canal, the extremities of which are distinct, though they approximate, 

 in consefxucnce of its curvatare (anopisthia.) They have no lorica ; 

 when free, they are solitary, but when attached to a pedicle they are 

 social, often assuming elegant ramose forms, like little trees, an 

 animalcule surmounting and terminating each branch or jjedicle. 

 These arborescent clusters are produced by imperfect self.division, 

 (see Plates 5 and 22.) 



The animal organization of this family is very distinct, with the 

 exception of vessels and nerves. All the species possess numerous 

 ciHa ; those of Stentor are covered with them ; others have them at 

 the mouth, where they are mostly disposed in the form of a wi'eath; 

 and by their vibratile action locomotion is eifected. In some genera, 

 as in Vorticella, Carchesium, and Opercularia, longitudinal and trans- 

 verse muscles ai'e seen. The polygastric nutritive apparatus may be 

 observed in all the genera, by feeding them upon artificial colouring 

 food. The course of the alimentary canal has been observed in all 

 the genera, except Trichodina and Urocentrum ; the mouth and dis- 

 charging opening, both lying in the same lateral cavity, have also been 

 demonstrated in all. The sexual system is [hermaphrodite, and 

 self-division is known in all; in Zoothamnium it is rare. In four 

 genera self-di^ision is imperfect ; hence they form beautiful little tree- 

 lilie clusters. Another mode of propagation is observable, namely, 

 the growth of gemmae on the side of the animalcules, or of their 

 pedicles. Although a system of sensation is not indicated by the 

 presence of eyes, we may presume its existence by their great irri- 

 tability when aj)proached. 



Some systematists consider that this family affords a connecting 

 link between the classes Polygastrica and Rotatoria. 

 ' This account of the organization of VorticelUna, chiefly from Ehren- 

 berg, must, according to later, and most pains taking investigations 

 of other natui-alists, be much modified. The result of those 



