THE SARCODINA 



91 



suggested that the pseudopodia in some forms are not motile, but 

 prehensile organs, and are withdrawn after a full meal (Actinosphcz- 

 ridium pcdatum). In some cases, at least, the pseudopodia apparently 

 paralyze the prey, for flagel- 

 lates or ciliates, coming in .,1 

 contact with the sharp pseudo- 

 podial tips, are immediately 

 stunned and lie quiet, while 

 either the pseudopodia lose 

 their rigidity and bend around 

 them, or smaller and new pseu- 

 dopodia are formed from the 

 body-substance, gradually sur- 

 round the prey, and draw it 

 into the body (see Fig. 18, p. 

 49). In the shelled forms the 

 process of engulfing prey is 

 less simple, and where there is 

 a distinct cuticle the ingestion 

 •of the food can take place only 

 by the softening or disappear- 

 ance of some part of the 

 membrane. In the shell-bear- 

 ing Rhizopoda(Thecamcebina) 

 food ingestion is confined to 

 •one part of the animal, the 

 region about the mouth-open- 

 ing ; while in some Reticulari- 

 ida the prey is not carried 

 inside of the animal at all, but 

 seizure, ingestion, and diges- 

 tion all take place in the net- 

 work of protoplasm formed by 

 the anastomosed pseudopodia 

 (Fig. 50). In the shell-bearing 

 Heliozoa the outer coating 

 must be ruptured for the en- 

 trance of the food particles 

 {Penard). 



In all cases the food substance is subsequently inclosed within 

 a water vacuole, the liquid being taken in with the food (Dujardin, 

 '41 ; Le Dantec, '90; Metschnikoff, '83). The fluid of the vacuole, at 

 first nothing more than water similar to that in which the animal 

 lives, gradually becomes acid, and in it the food particles are slowly 



Fig. 50. — Gromia oviformis Duj. [M. SCHULTZE.] 

 Some of the reticulate pseudopodia have captured 

 a diatom. 



