188 



BIOLOGY OF THE PROTOZOA 



Arcella, a diatom or other food body. Ingestion by "circumflu- 

 ence" appears to be due to a stimulus emanating from a living food 

 body, the effect of which through the motor response (Jennings, 

 1904) is to cause pseudopodia to flow toward the prey and to entrap 

 it while still at some distance from the body of the captor as in the 

 testate rhizopods, Foraminifera and Choanoflagellates where an 

 endoplasmic projection forms a pseudopodium which engulfs the 

 prey and then withdraws within the endoplasm where the prey is 



Fig. 99. — Two types of ciliated carnivores. A, Spathidium spathula about to 

 ingest a Colpidium colpoda; B, Lionotus fasciola swallowing a Colpidium colpoda. 



(Original.) 



digested (De Saedeleer, 1927 and 1929; Ellis, 1929). "Invagina- 

 tion" occurs in forms having a somewhat resisting periplast-like 

 ectoplasm such as Amoeba terricola according to Grosse-Allermann 

 (1909). When a living organism comes in contact with the surface 

 at any point, the local ectoplasm with prey attached sinks into the 

 endoplasm as though " sucked "in, the ectoplasmic walls being trans- 

 formed into endoplasm, while the ectoplasm about the area of 

 ingestion comes together sphincter-like, and fuses again to a smooth 

 surface. So, too, in A. proteus where, according to Mast (1916 and 



