38 GENERAL ORGANIZATION OF THE PROTOZOA 



PHYLUM PROTOZOA/ 



Subphylum SARGODINA. Protozoa showing no connections witli the bacteria, 

 usually of simple structure and characterized mainly by motile organs in the 

 form of changeable protoplasmic processes — the pseudopodia. 



Class I. RHIZOPODA. Sarcodina without axial filaments in the pseudopodia, 

 which may be lobose, filose, or reticulose. 



Subclass 1. Proteomyxa. Minute organisms with soft, miscible pseudopodia, 

 which anastomose upon touching; the cells unite at times to form plasmodia; 

 frequently parasitic. 



Typical genera: Gymnophrys, Cienkowsky, 1876; Pontomyxa, Topsent, 1893; 

 Vampyrella, Cienkowsky, 1876; Pseudospora, Cienkowsky, 1876; Plasmo- 

 diophora, Woronin, 1878; Nuclearia, Cienkowsky, 1876. 



Subclass 2. Mycetozoa. Pseudopodia-forming single cells which fuse to form 

 plasmodia, the latter often of great complexity. There are so many charac- 

 teristics of the fungi in the organisms of this group that their systematic posi- 

 tion is unsettled ; botanists include them with the fungi as a primitive group 

 under the name Myxomycetes or slime moulds. 



Order 1 . Acrasi-^i:. The single cells unite to form a common mass, but the cells 

 do not fuse, hence a pseudoplasmodium is formed which is enclosed in a 

 gelatinous mantle. 



Typical genera: Copromyxa, Zopf, 1885; Acrasis, Van Tieghem, 1880; Dic- 

 tyostelium, Brefeldt, 1869. 



Order 2. Filoplasmodia. The aggregated cells are not firmly united, but 

 remain connected for the most part by delicate threads of protoplasm. 



Typical genera: Labyrinthula, Cienkowsky, 1876; Chlamydomyxa, Archer, 1875. 



Order 3. Myxomycetes. The aggregation of the cells is here complete and often 

 results in the formation of complex fructifications in which hygroscopic threads 

 play an important part in scattering the often flagellated spores. 



Typical genera: Fuligo, Haller, 1768; Craterium, Trentepol, 1797; Stemonitis, 

 Gleditsch, 1753; Didymium, Schrader, 1797. 



Subclass 3. Foraminifera. Rhizopoda with fine branching and anastomosing 

 pseudopodia which form an irregular network around the entire body or parts 

 of it. Shells, when present, are calcareous, provided with many pores (Per- 

 forina) or without pores (Imperforina), and consist of one chamber (Mono- 

 thalamous) or of many chambers (Polythalamous). Rigid diagnoses are here 

 impossible, for the limits of the orders are ill-defined, and in some cases it is 

 difficult to accurately place organisms which are sometimes grouped as fora- 

 minifera, sometimes as test-bearing amebfe. The classification adopted here 

 is that of Lister, 1903. 



Order 1. Gromiida. (Fresh-water test-bearing forms removed.) The cell cover- 

 ing is simple and for the most part without calcareous deposits; chitinous 

 and single chambered. 



Typical cjencra: Gromia, Dujardin, 1835; Microgromia, Hertwig, 1874; Diplo- 

 phrys, Barker, Shepheardella, Siddall, 1880; Platoum, F. E. Sch., 1877. 



Order 2. Astrorhizida. Lister recognizes four families. Here the test is com- 

 posite, large, and monothalamous; the walls are formed of chitin with firmly 

 attached particles of sand, mud, sponge spicules, etc. 



' The classification adopted for a group of animals or plants in which life histories are but 

 little known and relationships obscure must be of a tentative nature, and the one here sug- 

 gested, while indicating relationships as they appear with our present knowledge, is only a^ 

 snap shot, as it were, of a growing subject and makes no claim of finality. 



