lSli 



BIOLOGY OF THE PROTOZOA 



it strikes a Paramecium or other ciliate purely at random; the 

 proboscis with seizing organ is buried in the victim which is then 

 swallowed whole (Fig. 98, 1-6). Lionotus fasciola, Spathidium 

 spathula and other gymnostomatous ciliates capture living organ- 

 isms in a similar way (Fig. 99) while less spectacular methods are 

 employed by Frontonia leucas, Ophryoglena flava, Prorodon niveus, 

 etc., in swallowing diatoms, desmids and other relatively stationary 

 organisms. 



A special type of food-getting, illustrated by the Rhizopods, may 

 be interpreted in some cases as the result of physical properties of 

 semifluid bodies. Rhumbler has made the most exhaustive studies 



>M 



Fig. 97.— Types of food 



getting. A, Acanthocystis (after Penard) ; B, Oicomonas 

 termo (after Biitschli). 



of food ingestion in these forms and distinguishes four types, viz.: 

 Ingestion by (1) "circumvallation," (2) "circumfluence," (3) "invag- 

 ination" and (4) " importation." Food-taking by " circumvallation" 

 is illustrated by Amoeba yroteus and usually takes place at that por- 

 tion of the body which, for the time being, is posterior. According 

 to Hofer (1889), Schaeft'er (1917) and others, the body becomes 

 anchored to the substratum by the secretion of an ectoplasmic 

 gelatinous substance; then, through the physical stimulus (Schaeffer, 

 1917) produced by a moving object (even a moving needle point 

 according to Verworn, 1889), walls of protoplasm flow out on either 

 side of the object and meet around it, thus enclosing a rotifer, an 



