RHIZOPODS, ACTINOPODS, SLIME MOLDS, SPOROZOA 77 



studies on Hyalodiscus simplex (Fig. 29, PL VIII). In this relatively 

 small ameba, viewed with the light microscope, the granular 

 endoplasm occupies a spheroidal hump while the clear hyaloplasm 

 surrounds it and forms a broad, flat anterior lobe or numerous 

 small pseudopodia. Constant streaming of particles within the 

 endoplasmic hump indicates that it is of fairly low viscosity. No 

 sharp boundary exists between endoplasm and hyaloplasm ; rather, 

 a transition zone appears, wherein particles are displaced con- 

 tinuously or in little hernias towards the ectoplasm. In the 

 hyaloplasm itself, the absence of inclusions prevents light- 

 microscope discrimination of gelated and solated zones ; however, 

 the behavior of the exclusively hyaline pseudopodia proves that 

 local transformations occur. 



The light, nearly homogeneous texture of the cytoplasm 

 described earlier is seen in Wohlfarth-Bottermann' s electron 

 micrographs around pinocytosis vesicles and in small pseudopodia 

 where active flow presumably was occurring at the moment of 

 fixation. Areas presumed to be gelated display a fine, compact, 

 but not detectably orderly, net-like structure, and a continuous 

 spectrum of intermediate conditions can be seen. Interestingly, 

 many submicroscopically small pseudopodia are present on both 

 dorsal and ventral surfaces of cells fixed in situ during locomotion 

 on a glass surface, indicating that contact with the substrate occurs 

 only at pseudopodial tips and that advance is stepwise rather than 

 an overall rolling or flowing process. 



The narrow transition zone between the hyaline layer and the 

 endoplasm in Hyalodiscus shows merely a scattering of cytoplasmic 

 particulates that become more abundant in the endoplasm. The 

 ground substance of the latter is a loose granular reticulum 

 resembling an intermediate condition seen in parts of the 

 ectoplasm. 



In earlier papers, Wohlfarth-Bottermann (1959a) and Schneider 

 and Wohlfarth-Bottermann (1959) reported that in many different 

 kinds of cells the gelated condition, or a state of high viscosity, is 

 correlated with an increased compactness of the ground substance. 

 Where active protoplasmic streaming is believed to be in process 

 at the time of fixation, the cytoplasmic ground substance appears 

 looser in texture. In some instances the compactness clearly 

 accompanies general withdrawal of cytoplasmic water, as in the 



