68 



THE PROTOZOA 



akoff ('88) describes three, Penard ('90) no less than four in Englypha, 

 and Rhumbler ('98) the latter number in Cyphoderia. Schewiakoff 

 ('88), apparently on very good grounds, maintained that certain spe- 

 cific functions characterize each of these zones, indicating, in a general 

 way, a regional differentiation and division of physiological labor. To 

 the outer zone, which corresponds to the ectoplasm of Amceba, he 

 ascribed a locomotor function, this being the seat of pseudopodia for- 

 mation ; to the second zone, which contains the nucleus, the function 

 of assimilation, and to the third zone a reproductive function. Penard 

 and Rhumbler separate Schewiakoff's second zone into two on account 

 of certain structural differences. According to these observers the 



Fig. 32. Actinophrys sol Ehr. [BiJTSCHLi after GRENACHER.] 



The axial filaments (a) extend through the endoplasm to the membrane of the nucleus ; c, a 

 contractile vacuole in the ectoplasm ; g, an ingested food particle in a gastric vacuole. 



outermost zone is distinctly vacuolated, the second contains food-par- 

 ticles in the process of digestion, the third, granules which represent 

 waste matter not determined, and the fourth, excretory granules. 



The appearance of the protoplasm in Heliozoa or Radiolaria is 

 quite different from that of the Rhizopoda. Ectoplasm and endoplasm 

 can be distinguished, but unlike the hyaline ectoplasm of Amceba, the 

 outer plasm of Heliozoa is made up of vacuoles much larger than 

 those of the endoplasm, the walls of these vacuoles being distinctly 

 granular (Fig. 32). The extremely vacuolated appearance, however, 

 seems to be largely dependent upon the medium in which the animal 



