212 DESCRIPTION OF {Polt/gasiHca. 



Akcella disphcera. — Oblong ; almost divided into two by a central 

 constriction ; one-half nearly occupied by tlie large foramen. 



A. econiis. — large ; hemispherical, not areolar ; aperture roimd, 

 large, placed to one side, entire. 



A. limata. — Lorica sub-globose, large ; Avith a large semi-lunar 

 opening, seated to one side. 



A. Nidus-pendulus. — ovate ; oblong, hyaline, loosely areolated ; 

 aperture in front, oblong, margin entire. 



A. pileus. — Lorica hemispherical, depressed, reddish, minutely and 

 elegantly areolar ; apcrtui'c centi'al, circular. 



A. ? glolulus. — Sub-globose ; with loosely reticular lines, appearing 

 granular; aperture large, simple. Diameter l-730th. Found on 

 moss at Berlin, Potsdam, &c. 



A. granulata. — Oblong; hyaline. Has the habit and size of A. 

 hyalina with a granular instead of a smooth surface. Length 1 -940th. 

 On moss in Hercynia, &c. 



A. caudicola. — Lorica ovate, oblong, rounded at each end, hyaline, 

 very delicately hispid, not areolar ; aperture anterior, round, large. 

 Length 1 -840th. 'K-eihit oi A. Nidus peridulus. Foimd in Venezuela, 

 on roots of plants, such as ferns, &c. 



Genus Cyphidium. — This genus is distinguished by the creatures 

 having only one dilated variable ]3rocess, and a lorica of the form of a 

 pitcher, with protuberances issuing from it. It forms a connecting 

 group between Arcella and Bacillaria, by reason of the sijuple loco- 

 motive organ (like a snail's foot), and approaches very closely to the 

 group Desynidiece. The lorica is something like a little die or stamp, 

 mounted upon a short stem. It is very irregularly formed, having 

 protuberances so as to make it appear four-comered ; it is combustible. 

 The oi'gan of locomotion is a broad, gelatinous, variable process, with 

 smooth edges, resembling in appearance the body of Amceba verrucosa. 

 Neither digestive cells or apertures in the lorica have yet been ob- 

 served, nor organs of sensation, or of propagation. 



C. aureolum. — Lorica of a cubical form, with protuberances ; process 

 colourless. In March, 1835, says Ehi^enberg, "I first observed 

 hundreds of these crcatm-es in a glass of water, which had stood 

 throughout the winter, in company with some specimens of the 

 Micrasterias. I'reviously to discovering tliese, the Amoeba verrucosa 



