Arcelliiia.] infusorial animalcules. 205 



is imknoAyn, neither has increase by self- division, by the formation 

 of gemmae, or otherwise, been recognized. 



The shell or loriea of the Arcellina or Rhhopodes, varies much in 

 figure, and especially in the condition of its siu'face, which may be 

 smooth, or variously, and oftentimes beautifully sculptured, or beset 

 with spires or other prominences. The Rhizopoda have a close 

 affinity to the Pohjthahmia or Foraminifera ; indeed, some authors, 

 as Dujardin and Schlumberger, describe as ^Azko/?oic;s, several genera 

 placed by others — Ehrenbcrg, D'Orbigny, &c., among the Pohj- 

 thalamia. These doubtful genera include beings with more complex 

 loricse, than those strictly of an Infusorial character. 



In determining the various species of Arcellina, the dimensions, 

 figiu-e, and other circumstances pertaining to the opening (mouth) 

 of the loriea, are of gi'eat importance. The loricae may often be 

 foimd empty, they may be frequently seen tinted orange-yellow, or 

 brown ; theu- consistence also varies, fi'om a flexible parchment-like 

 material, to a brittle siliceous (calcareous) substance. Some of 

 the Rhizopoda attain such dimensions, as to nearly fall within the 

 compass of unaided vision. 



Some are marine ; others as the Bifflugia, live in fresh water. 

 Concerning their habit, we may quote Dujardin's account, who 

 says ; " The Rhizopodes being deprived of the power of swimming, 

 and compelled to merely crawd (glide), when not fixed to the surface 

 of bodies, are consequeutly to be met with only upon aquatic 

 plants, between the leaves, which afford them shelter, or in the 

 stratum of debris, about the base of such plants, or between the 

 asperities of the shells of marine mollusks. They are not met 

 with in infusions, although they Avill live a long time in bottles con- 

 taining any plants, which may serve them for an abode, and in such 

 cases they will very soon be found crawling on the surface of the 

 glass, and be easily observed." 



Speaking of the afiinities of the Foraminifera, D'Orbigny remarks, 

 " From what precedes concerning the characters of the Foraminifera, 

 it is. evident they cannot be arranged under any known class of 



animals Their place in the animal kingdom is, as au 



altogether independent class between the Echinodermata and Polypes ;^^ 

 (Foramiuiferes fossiles du Bassin, Tertiare de Vienne, p. 17, 1846.) 



