202 ] The Classification of Lower Organisms 



Proteus; Amiba divergens Bory Diet. Class. Hist. Nat. 1: 261. 1822; Amoeba Proteui 

 Leidy). It appears that MiiUer intended to rename the Chaos Protheus of Linnaeus; 

 that in 1773 he actually did so; but that in 1786 he applied another new name to a 

 different organism. Ehrenberg's amended spelling Amoeba, although in general use, 

 is not valid as that of a generic name; as Schaeffer suggests, the word may be used as 

 a common noun. Amiba diffluens is uninucleate; large, but not visible to the naked 

 eye. 



In nuclear division in the common amoebas the nuclear membrane disappears. 

 There are many chromosomes in a blunt-ended spindle. Short (1945) noted a pecu- 

 liar twisting of the spindle of Chaos Protheus. 



Schaeffer included in the present family three further genera, Trichamoeba Fro- 

 mentel, Polychaos Schaeffer, and Metachaos Schaeffer. Here, in ignorance of its 

 relationships, another well-known genus is assigned to this family. 



Pelomyxa, typified by P. palustris Greeff ( 1874) , resembles Chaos Protheus in being 

 exceptionally large, macroscopically visible, and multinucleate. It is definitely dif- 

 ferent from Chaos Protheus in manner of movement (King and Jahn, 1948) and in 

 chemical characters (Andressen and Holter, 1949). 



Minute amoebas moving by means of a single pseudopodium are called Vahlkamp- 

 fia. They are believed to have swimming stages with paired equal flagella. If so, they 

 do not belong to the present group, but perhaps to the plant kingdom. 



Family 2. Mayorellida [Mayorellidae] Schaeffer in Publ. Carnegie Inst. 345: 47 

 (1926). Producing numerous brief conical pseudopodia, but moving by a single large 

 clear one. Mayorella, Pontifex, and several other genera proposed by Schaeffer; 

 Dactylosphaerium Hertwig and Lesser; Dinamoeba Leidy? The last may be the non- 

 flagellate stage of Chactoproteus Stein. 



Family 3. Thecamoebida [Thecamoebidae] Schaeffer op. cit. 83. Amoebas with a 

 tough pellicle simulating a shell, moving by the outflow of clear protoplasm at the 

 anterior margin. Thccamocba Fromentel. Rugipes Schaeffer. 



Family 4. ''Hyalodiscida [Hyalodiscidae] Poche in Arch. Prot. 30: 182 (1913). 

 Family Cochliopodiidae de Saedeleer in Mein. Mus. Roy. Hist. Nat. Belgique 60: 5 

 (1934). Similar to the foregoing but without the tough pellicle. Commonly dome- 

 shaped, with a row of small pseudopodia projecting from the margin. Hyalodiscus 

 and Cochliopodium of Hertwig and Lesser, together with certain genera of Schaeffer. 



Family 5. Endamoebida [Endamoebidae] Calkins. Entozoic amoebas. 



Endamoeba Leidy is found in cockroaches and termites. The nucleus contains no 

 karyosome, but many separate granules; in mitosis, definite chromosomes arc formed 

 (twelve in E. disparita), but there is apparently no centrosome; at least, no intra- 

 desmose is seen (Kirby, 1927). 



Entamoeba Casagrandi and Barbagello, named at nearly the same time as the fore- 

 going and regrettably similarly, is widely distributed in invertebrate and vertebrate 

 hosts. E. dysenteriae (Councilman and Lafleur) Craig {Endamoeba histolytica Schau- 

 dinn) is a serious pathogen to man, the cause of amoebic dysentery. E. coli and E. 

 gingivalis are believed to be harmless commensals. The fully mitotic character of 

 nuclear division in these organisms was established by Kofoid and Swezy ( 1921, 1922, 

 1925). The nucleus contains a small karyosome and an intranuclear centrosome. Mi- 

 tosis begins with division of the centrosome into two, which remain connected, as they 

 draw apart, by a stainable strand, the intradesmose (the term is of Kofoid and Swczy, 

 1921). The karyosome breaks up into chromosomes, six in the species mentioned. 

 Spindle fibers connecting these to the centrosomes have been seen; Child (1926) 



