THE SAKCODINA 



81 



character can have but little value. Despite the uncertainty of the 

 pseudopodia as a basis of classification, their structure among the 

 Rhizopoda is frequently so characteristic that the identification of 

 some species of Amoeba is comparatively easy. Thus Amoeba proteus 

 has large and blunt pseudopodia in the adult phase, while the young 

 form (known as A. radiosa) 1 has sharper, stiffer, and hyaline 

 pseudopodia. When a pseudopodium of A. proteus starts from 

 the periphery, it continues as a stream until, as a rule, a long, 

 lobose structure results. When, however, a pseudopodium of A. 

 blatta Biitschli or of A. limicola Rhumbler starts from the periphery 

 of the spherical body, it resembles a miniature eruption. A break is 



Fig. 45. Camptonema nutans. [SCHAUDINN.] 



The axial filaments extend throughout the endoplasm (A), taking their origin at the nuclear 

 membrane (B). x, an axial filament highly magnified. 



made on the periphery, and through it the granular endoplasm flows 

 down the sides of the spherical body instead of outward into elongate 

 pseudopodia (Fig. 44, A, B). In such cases the pseudopodia may be 

 used to identify the organism. 



The pseudopodia of the Heliozoa and the Radiolaria are far more 

 complicated than those of the Rhizopoda. They usually have dis- 

 tinct axial filaments, consisting of some unknown substance, extending 

 throughout the entire length, and even into the endoplasm, where 

 they not infrequently abut against the membrane of the nucleus or 

 meet at a common centre (Actinophrys, Acanthocystis). The granular 

 protoplasm which surrounds the axial filament is in constant but slow 

 streaming motion. The point of interest is the axial filament, which 

 is not strictly comparable with the skeletal parts, but is probably stif- 



l Cf. Scheel ('99). 



