OF THE PHYTOZOA. 129 



at present a detailed review, we will confiue ourselves to a few general obser- 

 vations on the nature of the several families brought together under the head 

 of Phytozoa. The Monadina (XYIII.) of Ehrenberg comprise a multitude of 

 beings differing widely among themselves, and, for the most part, not placeable 

 with certainty either among plants or animals. Of the genus Monas, especially, 

 it may be said that its species are, with few or no exceptions, mere phases of 

 being of other organisms. Of other genera the like may be presumed, although 

 the organisms in whose cycle of life they enter as one of the links have not 

 been determined. Not a few are doubtless zoospores of Algae or of micro- 

 scopical Fimgi. 



Uvella (XVIII. 5) is, in the opinion of most authorities, a vegetable struc- 

 ture (see p. 134) ; but Cohn (Entw. p. 115) still seems disposed to consider it 

 an animalcule, and represents Anthophysa (see p. 135), which has likewise 

 been extensively believed to be a parasitic Alga or Fungus, to be an animal 

 Uvella sm^mounting a branching stem. Polytoma is another disputed posses- 

 sion between zoologists and botanists : among the most recent advocates of its 

 animal character is Schneider (see pp. 136-139). 



The Cryptomonadina would, in the language of naturalists generally, be 

 called ' encysted ' Monadina, and, like this family, are divisible into true 

 vegetable and into doubtful animal organisms, the former certainly prepon- 

 derating. The next two families, Volvocina and Vihrionia, and more especially 

 the former, may without hesitation be counted with plants, whilst the remain- 

 ing one, Asfasicea, the majority of naturalists reckon among animalcules. 



Habitats. OccmEENCE in masses. Colour caused by theie accumula- 

 tion. — By far the majority of known Phytozoa are of a freshwater habit ; 

 yet it may be that, were the search as diligent, marine species might be 

 found in nearly equal abundance, particularly in inland and shallow seas, 

 gulfs, or lakes affording appropriate habitats for the larger Algae. Monads 

 and Vibrios, Bodos, and the Cyclidia of Dujardin, are probably the most 

 abundant and widely diffused of all created organisms, — a fact not remark- 

 able when it is considered that those genera represent the primary or ger- 

 minal stage of so many organized beings, both animals and plants. They 

 make their appearance, in collections of water and in infusions, before all 

 others, and, unlike most microscopical creatures, find a fitting habitat in foul 

 or decomposing fluids as well as in sweet water. They also propagate them- 

 selves with such astonishing rapidity, that the fluid or other medium in 

 which they occur becomes coloured by them. However, this very rapid de- 

 velopment, and this capability of colouring the siuTOunding medium, are not 

 restricted to the genera named, but are partaken by others among the Phy- 

 tozoa, — for example, Uvella, Astasia, Euglena, and the genera of Volvocinece, 

 aU of them denizens of pure water, incapable of existence in impiu'e, stagnant, 

 and decomposing liquids. 



The coloiu' presented by their accumulation in large numbers, varies 

 according to the species. Thus, the Astasia hcematodes and Euglena san- 

 guinea give a blood-red colour to water. The Monas (Vibrio) prodigiosa is 

 stated by Ehrenberg to be the cause of the blood-hke spots which have made 

 their appearance at times in bread and meal, much to the consternation and 

 dismay of the ignorant and superstitious ; and, again, the Hcematococcus or the 

 red-coloured stage of the Hysginum of Perty is the cause of the phenomenon 

 of red snow. A green colour is much more frequent, and due to a larger 

 variety of Infusorial organisms ; such are Moyias bicolor, Uvella Bodo, Cryp- 

 tomonas glauca, Gonium, Chlorogonium, Eiiglena viridis, Chlamydomonas, 

 Pandorina, Volvox, Stephanosphcera, and others. 



Besides becoming thus obvious to common observation by their colour. 



