146 NATURAL HISTORY 



ing : it occasionally appears indented, but its definition 

 is difficult, from the motion of the intervening cilia, 

 which sometimes move erect, and at others are curved 

 outwards. 



347. VoRTiCELLA utricuhta, — The bottle-shaped Vorti- 

 cella, shewn at figure 208, appears so closely allied to the 

 preceding one, that I have introduced it here. It is of 

 a green colour^ and no interior projection or nipple is 

 observable ; the body and neck are capable of consider- 

 able extension and contraction, and the rotatory cilia are 

 either erected or deflected at the pleasure of the animal- 

 cule. Found in salt-water. 



348. VoRTicELLA sputarium. — This animalcule assumes 

 appearances so different, according to the position in 

 which it is viewed, that it is difficult to present a clear 

 idea of it : in swimming, if viewed sideways, it appears 

 cylindrical, the anterior being dilated, and the posterior 

 contracted and convex : a series of long radial cilia may 

 be observed, and the body of the animalcule appears a 

 globular opaque mass. Found at the end of summer 

 among lemna, 



349. VoRTiCELLA polymorpha, V. multiformis, and V. 

 stentoria, 1 am inclined to believe, are only varieties of 

 the same species. By their great powers of extension 

 and contraction, and also by their being sometimes at- 

 tached to the surface of vegetable or other substances, 

 and at others swimming freely, they assume such different 

 characters, that unless attentively watched they may be 

 easily mistaken for different animalcules. The Leuco- 

 phrys cornula (226) is probably allied to them, as 



