PHYLUM PROTOZOA 



57 



which is traceable through the general protoplasm as far as the 

 nucleus. Living organisms are de- 

 voured in much the same way as in 

 Amoeba: each is ingested along with 

 a droplet of water, and is thus seen, 

 during digestion, to lie in a de- 

 finite cavity of the protoplasm, 

 called a food-vacuole. If the or- 

 ganism be small, processes of the 

 protoplasm are developed, and sur- 

 round and engulf it. If it be larger, 

 several pseudopods are applied to 

 it, their axial fibres becoming ab- 

 sorbed, and their substance envelops 

 it, enclosing it in a vacuole. The 

 animal can fix itself by means of 

 its pseudopods, the ends of which become viscid, and it is able 

 to crawl slowly by their means. Sometimes it floats freely in the 



FIG. 3<t Actinophrys sol. a. axial 

 filaments of pseudopods ; n. nucleus ; 

 p. pseudopod. (From Lang's Com- 

 parative Anatomy, after Grenadier.) 



Tnecl 



chr 



FIG. 40. Actinosphserium eichhornii. A, the entire organism; B, a small portion 

 highly magnified ; chr. chromatophore ; cort. cortex ; c. roc. contractile vacuole ; med. medulla ; 

 nu. nuclei. (From Blitschli's Protozoa, after Hertwig and Lesser.) 



water, and it possesses the power of rising or sinking by some 

 unknown means. 



Actinosphcerium (Fig. 40, A), another fresh-water form, is more 



