190 



THE PROTOZOA 



According to Rhumbler (204), with a more fluid condition of the 

 ectoplasm, the food is ingested by import or circumfluence ; when 

 the ectoplasm is stiffened to a membrane-like consistence, the 

 ingestion is effected by circumvallation or invagination. Rhumbler 

 maintains that all known methods of food-ingestion by amoebae, as 

 well as their movements, can be explained mechanically by differ- 

 ences of surface-tension in colloidal limiting membranes, and can 

 be imitated artificially in substances that are not living. 



Fio. 82. Ingestion of a food-particle by " invagination " in Amoeba terricda. 

 A E, Five stages of the process, semi-diagrammatic ; F, diagrammatic 

 figure to show the direction of the currents on the surface of the body of the 

 amoeba during the process of ingestion. After Grosse-Allermann (245). 



In corticate forms the ingestion of food is limited to one or more 

 special openings or organs, in which a direct communication is 

 established between the fluid endoplasm and the surrounding 

 medium, as in the cytostomes of Flagellata and Ciliata and the 

 suctorial tentacles of Acinetaria. 



The digestion of the food is effected within the protoplasmic body, 

 and as a rule the prey is taken bodily into the cytoplasm ; but 

 the Acinetaria have the power, not fully explained, of sucking out 



