RHIZOPODS, ACTINOPODS, SLIME MOLDS, SPOROZOA 73 



morphologists have turned to some of the abundant smaller 

 species in related families, as being less spectacular but perhaps 

 more representative both as rhizopods and as cells than their 

 enormous cousins. Among the smaller forms, Hyalodiscus simplex 

 (Wohlfarth-Bottermann, 1960b), Hartmannella rhysodes (Pappas, 

 1959), Acanthamoeba sp. (Mercer, 1959), and Hartmannella astronyxis 

 (Deutsch and Swann, 1959), and the parasitic amebae, Entamoeba 

 invadens (Barker and Deutsch, 1958; Deutsch and Zaman, 1959; 

 Zaman, 1961), E. histolytica (Osada, 1959; Wohlfarth-Bottermann, 

 1959a), and Endamoeba blattae (Beams, Tahmisian, Devine, and 

 Anderson, 1959b) have received at least passing attention. Chief 

 sources of data on Amoeba and Pelomyxa are papers by Lehmann 

 and his colleagues (1950, et seq.\ Bairati and Lehmann, 1952, 

 et seq.\ Pappas (1956a, 1956b, 1959), Cohen (1957), Greider, 

 Kostir, and Frajola (1958), Mercer (1959), Schneider and 

 Wohlfarth-Bottermann (1959), and Roth (1960a). 



The mobile surface membrane or plasmalemma consists of a 

 unit membrane coated on the outer side (at least in Amoeba, 

 Pelomyxa, and Hyalodiscus [Fig. 29, PL VIII], but not in some 

 of the small amebae) with a diffuse, low-density layer of material 

 bearing a continuous fringe or pile of very fine, hair-like exten- 

 sions. These filaments, measuring 5 to 15 m/x in diameter and 

 up to 150 m/x in length, are darkened by phosphotungstic-acid 

 staining. Their dimensions suggest filamentous macromolecules, 

 and their presence on the cell surface (where cytochemical tests 

 show the occurrence of polysaccharide as well as protein) has 

 prompted guesses that they are mucoproteins serving for adhesion 

 to a substrate or to particulate food (Lehmann, Manni, and 

 Bairati, 1956), and that they function in the surface binding of 

 substances in solution shown to occur prior to pinocytosis (see 

 discussion in Chapter 2). The hairy coating is very quickly lost 

 from the surface of a newly formed food vacuole membrane 

 (Roth, 1960a) but apparently persists at least for a limited time on 

 deep pinocytosis channels and vesicles. It seems to be markedly 

 reduced on the body surface of dividing Amoeba (Roth, Obetz, 

 and Daniels, 1960); at this time the cell assumes a roughly 

 spherical form, called the mulberry stage, with an all-over lumpy 

 surface. 



The cytoplasmic ground structure of amebae is of compelling 



