488 SYjSXEilATIC HISTORY OF THE INFUSORIA. 



" These generic distinctions are, however," Diijardin veiy justly adds, " en- 

 tirely artificial, and simply intended to facilitate the naming of Infusoria one 

 may have met with in such and such an infusion, and which, when better 

 known, may prove in some instances only varieties of a single species." 



Perty appends to his history of Monadina the following observations : — 

 " Ehi'enberg's Monadina are very difficult to determine ; many, hke Monas 

 bicolor, M. CoJpoda, M. Enclielys, M. Umbra, M. Tiyalina, M. ovalis, M. Mica, 

 M. cylindrica, M. cleses, M. flavicans, M. simplex, M. inanis, and M. scintiUans, 

 appear to be only the earher stages of other Monadina, or the yoimg stages 

 of Ciliata. M. Crepuseulum forms my genus Acariceum; M. Termo is a 

 Cercomonas ; M. Guttula and M. vivipara are most likely varieties of the 

 multiform M. Lens ; M. grandis and Mieroglena monadina are Sporozoids ; 

 Monas ocliracea, M. eruhescens, M. vinosa, and probably M. gliscens belong to 

 the genus Chromatium (XIX. 1) ; M. Punctum is no other than the one fila- 

 mentary variety of Polytoma ; M. socialis goes along with Cercomonas ; M. 

 tingens is the young condition of Chlorogonium euchlorum ; Uvella virescens 

 possesses one filament and no cilia ; U. Uva may be a coloui'less variety 

 of it ; U. Glaucoma scarcely belongs to the genus Uvella, as it has always 

 two filaments U. Bodo appears a developmental phase of Euglena viridis ; 

 Polytoma Uvella is equivalent to my P. Uva ; Mieroglena punctifera is un- 

 kno^vn to me. The genus Doxococcus I consider untenable ; D. ruber and B. 

 Pulviscidus are merely resting forms of Astasia ; Chilomonas Volvox and C. 

 destruens are in all probability embiyos of Ciliata, and Ch. Paramecium is the 

 hvahne variety of my Cryptomonas polymorpha ; and Bodo is di\isible into 

 Anisonema (XIX. 8)" and Cercomonas (XYIII. 11, 12, 20)." 



The new genera instituted by the Swiss naturahst are Tetramitus (XIX. 

 3), MaUomonas (XIX. 4), Pleuromonas (XVIII. 25), Spiromonas (XYIII. 

 24), Menoidium (XIX. 2), Chromatium (XIX. 1), and Acariceum. Fresenius 

 accepts two of these new genera, viz. MaUomonas and Tetramitus, and creates 

 in addition two others, Rhabdomonas and Grymcea, — the former not identical 

 with the Hhabdomonads (staff-like monads) mentioned by Ehrenberg as a 

 group of his genus Monas. 



Respecting the large contribution by Perty to the number of Monadina 

 catalogued by Ehrenberg and Dujardin, the question arises, whether the 

 forms named are reaUy different and distinguishable. We fear, indeed, that 

 the increased number will rather perplex and encumber the observer than 

 advance his real knowledge of microscopic forms. StiU, to make our resume 

 complete, they must be enumerated. In effecting this, the plan pm^sued wiU 

 be to describe the several genera admitted by Ehrenberg first, adding the 

 species noted by others, and after these to give the characters of genera and 

 species constituted by Dujardin, Perty, or any other naturalist: where the 

 same being has had a second name given it, it will be added as a sjTionym. 

 In the systematic details we shall preserve the descriptions and remarks in 

 general which appeared in the last edition, and are largely borrowed from 

 Ehrenberg's most valuable works. These, indeed, are eveiy^where tinged 

 with the peculiar hj-pothesis of that writer, the value and bearing of which, 

 however, have been sufficiently examined in the first part of this work to 

 render explanations and corrections here unnecessary. The description, 

 therefore, of mouths, eyes, stomach sacs, glands, vessels, hermaphrodite deve- 

 lopment, ova, and of all other stiiictui'es or organs of higher animal organiza- 

 tion, will have no other value as applicable to such special organs than that 

 accorded to it in the mind of eveiy indi\idual reader of the chapter on the 

 structure and functions of the Monadina, who can draw for himself his own 

 inferences from the facts and opinions therein recorded. 



