OF THE PEOTOZOA. EHIZOPODA. 235 



the calcareous natiu'e of those of the Pseudopodoiis class, is not in accordance 

 with fact ; for although all, or almost all, Polythalamla have calcareous shells, 

 yet the flexible loricse of many Monothalamia are chitinous, just as those of 

 loricated Ciliata. 



In the presumed fact of the shells of Arcellina being silicious, Ehrenberg 

 discovered a relation betTs^een that family and the Bacillaria. This affinity he 

 traced still further ; for, when describing the genus CyphkUum, he remarked 

 — '^ It forms a connectmg group between ArceUa and Bacillaria, by reason of 

 the simple locomotive organ (like a snail's foot), and approaches very closely 

 to the group Desmidieoi" However, even if he be right as to the single un- 

 divided process of Cyphidium, the presence of any extended foot or pedal 

 organ from the silicious fronds of EaciUaria, whether Diatomew or Desmidiece, 

 is not now admitted by any natui^alist. 



If Stein's observations and opinions be correct, an indirect relationship 

 actually exists between Ciliated Protozoa and Rhizopoda; for that pains- 

 taking observer has con\inccd himself that the VorticeUina, by ulterior de- 

 velopment, become transfoiTaed into Aciiieta-]ike or Actinophryean organisms, 

 of the intimate affinity of which no doubt can be raised. The questions 

 raised by this apparent transformation do not require discussion here, since 

 they are fiilly entered upon in the history of the Ciliata, and in that of the 

 Acinetina, considered as a subclass of Rhizopoda. 



Another alhance was formerly assigned to the Multilocular Rhizopoda, \-iz. 

 mth the Cephalapoda, of which they were treated as a subdi\'ision. This 

 association was suggested, by the ]Sfaidilus-]ike form of some genera, to the 

 earliest observers of the Foraminifera — Beccarius in 1731, and Plancus in 

 1739 ; and the error was perpetuated by D'Orbigny in 1826. Dujardin has 

 the great merit of first combating this mistaken opinion, and of pointing out 

 the extremely simple nature of their contents, and their true affinity with the 

 simple Amcebce. 



Several natui'alists, and among them M. de Quatrefages, have classed the 

 comparatively large Noctilucce with the Rhizopoda. But direct observation 

 seems to show that, although in a few particulars a likeness obtains, yet 

 the sum of the differences greatly surpasses that of the resemblances. The 

 Noctilucoi show a more complex organization ; they have an integument com- 

 posed of two layers, an evident mouth and gastric cavity with aj^pendages, 

 and motile filaments, but no variable processes. 



A striking general resemblance subsists between the ^N'aked Rhizopoda — 

 Amcebce — and the like isolated individuals and the germs of freshwater Sponges 

 or Spongilke, which Mr. Carter has named Proteans (XXI. 5 a, h, c). The 

 resemblances are well conveyed in the following quotation from Mr. Carter's 

 paper : — " A ragged portion torn off with a needle, will be seen gradually to 

 assume a spheroidal form ; and if there be a spiculum, it wiU embrace it within 

 its substance, it may even be seen to approach it, and it may bear away the 

 spiculum, having, as it were, spit itself upon it. On its circumference ^vill be 

 obsei-ved little papiUse, which gradually vary theii- form, extending and retract- 

 ing themselves, imtil one of them may be seen to detach itself from the parent 

 mass and go off to another object. This little animal, one of the group which 

 it has left, may remain stationary' on the second object, or descend to the 

 watch-glass, assuming in its progress aU forms that can be imagined, sphe- 

 roidal or polygonal, whilst every point of its body appears capable of ex- 

 tending itself into a tubular attenuated prolongation .... These transparent 

 little sacs (the gemmules of Grant and Hogg) are sometimes filled with green 

 matter. They appear to be able to adapt themselves to any form that may 

 be convenient for them to assume ; and when forcibly separated from each 



