THE SARCODINA 



. 



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

 prehensile organs, and are withdrawn after a full meal (Actinospha- 

 ridiuni pedatum}. In some cases, at least, the pseudopodia apparently 

 paralyze the prey, for flagel- 

 lates or ciliates, coming in 

 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 (Thecamoebina) 

 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 j\ ' 



Heliozoa the outer coating pig SQ _ Gromia mifannis Duj [M . ScHULTZEj 



must be ruptured for the en- Some of the reticulate pseudopodia have captured 



trance of the food particles adiatom - 

 (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 



