Arcellina.j infusorial animalcules. 207 



large opening in its lorica for the escape of the expansions ; the other, 

 by numerous genera, in all which numerous filiform expansions 

 emerge fi-om many distinct pores (foramina) ; hence the name 

 applied to them by D'Orbiguy, of Foraminifera, and by Ehrenberg, 

 of the Greek equivalent, Folythalamia. 



Of these porous animalcules, Dujardin cites but the subse- 

 quently named genera, viz , Vorticialis, Cristelh/ria, Rosalina, and 

 Planorbulina. 



Kcfcrcnce to the system advanced by Siebold, page 62 will show 

 that this naturalist in forming his class Rhizopoda, has included in his 

 family ArcelUna, the genera constituting the first and second tribes 

 of Dujardin, and has created an order, Polysomatia, for the undoubted 

 Polythalamial genera, Vorticialis, Geoponus and Nonionina. 



In the ensuing descriptions of the species Arcellina, we shall 

 confine ourselves to the beings embraced in the Arcellina of Ehren- 

 berg, and in the two fii-st tribes of the second section of the plan of 

 M. Dujardin. For an account of the Palythalamia or Foraminifera, 

 we may refer to the splendid work of D'Orbiguy, before named, and 

 to the various papers of that author, and of Professor Ehrenberg. 



Genus Ditflugia. The diffluent Animalcules. — This genus is cha- 

 racteiized by the creatures having the variable processes, -which issue 

 only from the fore part of the body, numerous, or each one cleft 

 into several parts, so as to give it the appearance of being many. 

 The body is enveloped in a horny pitcher-like lorica, sometimes glo- 

 bular, at other times oblong or spiral in form, and either smooth or 

 sculptured. The lorica of this genus being opaque, except in 

 D. enchelys, little of the internal organization of these creatures is 

 known ; in B. enchelys, numerous digestive cells have been seen. In 

 D. proteiformis and B. acuminata, the lorica is covered with grains 

 of sand, similar to that of the caddis- worm. In D. oUonga and 

 D. enchelys, the shell is smooth. 



D. proteiformis. — Lorica ovate and subglobose, as represented in 

 figs. 89, 90, and 91 : it is roughly coated with minute grains of 

 sand, and is either of a blackish or greenish colour. The transparent 

 processes vary in number from one to ten. In fig. 89, six are pro- 

 truded. M. Lc Clerc describes this species as having spu'al coixu- 



