PROTOZOOLOGY 



a short cyclosis in the posterior half of the body. In Carchesium, ac- 

 cording to Greenwood, the food-vacuoles pass down to one end of 

 the macronucleus and then move close along its concave surface to 

 the anterior end of the nucleus where defecation to the vestibule 

 takes place (Fig. 35). 



As stated above, in a number of species the food organisms are 

 paralyzed or killed upon contact with pseudopodia, tentacles or ex- 

 ploded trichocysts. In numerous other cases, the captured organism 

 is taken into the food vacuole alive, as will easily be noted by ob- 

 serving Chilomonas taken in by Amoeba proteus or actively moving 

 bacteria ingested by Paramecium. But the prey ceases to move in a 



Fig. 35. Diagram showing the digestion within the food vacuoles in 

 Carchesium polypinurn (Greenwood), a, digestion area; b, region of little 

 change; c, region of acid reaction; d, region of neutral reaction; e, defeca- 

 tion area. 



very short time. It is generally believed that some substances are se- 

 creted into the food vacuole by the protoplasm of the organisms, to 

 stop the activity of the prey within the food vacuole. Engelmann 

 (1878) demonstrated that the granules of blue litmus, when ingested 

 by Paramecium or Amoeba, became red in a few minutes. Brandt 



