58 GENERAL HISTORY OF 



tions, as A\'ell as Gon'mm, Pandorina, T'olvox, Frotococcus nivalis, &c., 

 j)reseut, in U13- oi)imon, characters of animality, too decided, and too 

 permanent for it to bo possible to refer tliem to tlie vegetable king- 

 dom ; and I think it Avonld prove more convenient to unite them, 

 with all the other Infusoria, fPolygastricaJ coloured green, in one 

 and the same group, which might be called Chlorozoidefe,''^ (Sec. IV.) 

 We have before (Sec. XII.) introduced the sweeping statement of 

 !M. Agassiz, and his opinion, that all the mouthless Infusoria are 

 nothing but various forms, and phases of development of Alga?. To 

 avoid repetition, we will also now refer to the same section for that 

 naturalist's views of the affinities of the other groups of Pohjgastrica. 



M. Braun would refer the Vohocina, (see remarks on that family, 

 Part III.) to the vegetable kingdom, believing them to be of the 

 same tj^e with certain Zoospores, which become composite by 

 fissiparous multiplication ; whilst Dr. Burnett, of New York, would 

 associate the Vihrionia (see that familj^) with such Algse as the 

 T'orula. 



Before proceeding with the affinities of the various Infusoria pos- 

 sessing mouths, we may seek those of the peculiar beings included in 

 Ehrenberg's families Amahcea and Arcellina, and known to many 

 naturalists as Pseudopoda and Rhizopoda. Their muco-gelatinous 

 substance is either naked or defended by a lorica. The fonner bear 

 the nearest resemblance to minute sponges, but differ, in representing 

 but a single individual, and not a complex aggregation, as do the 

 latter. However, these singular simple numerous masses, when 

 enclosed by a lorica, assume an affinity to a set of beings, often of 

 very elaborate external organization, known as PoJythalamia or 

 Foraminifera. This affinity is so close, that writers are not yet agreed 

 as to which class the Infusoria, or the Foraminifera, several genera, 

 ou<'ht to be referred. Thus, Trinema, Fuglyjyha, Rotalia, Vorticialis, 

 Cristellaria, kc, genera of Ehizopodes, according to M. Dujardin, 

 are included by M. D'Orbigny, among his Foraminifera. This 

 diversity of opinion must last until the essential characteristics, and 

 peculiar structure of Foraminifera are better kno-WTi. Ehi-enberg 

 designates them Polythalamia, and would employ, as a distinction 

 between them and his families, Arcellina, Difflugia, &c., the fact of 

 the calcareous composition of their shells, stating those of the latter 



