PHYSIOLOGY 87 



In the cytostome-bearing Mastigophora, the lashing of flagella 

 will aid in bringing about the food-particles to the cytostome, 

 where it is taken into the endoplasm. In the ciliates there are nu- 

 merous types of cytostomes and associated organellae. But food- 

 capturing seems to be in general of two kinds. When the cytostome 

 is permanently open, the organism ingests food-particles which 

 are small enough to pass the cytostome and cytopharynx, as in 

 the case of Paramecium. Another type is one, such as noted in 

 Coleps, Didinium, etc., where the ciliate attacks other organism 

 and sucks in the body substance of the latter through the en- 

 larged cytostome. 



The ingested food-particles are always surrounded by a film of 

 fluid which envelops the organism and the whole is known as the 

 food vacuole (p. 77). The quantity of fluid taken in with the 

 food varies greatly and, generally speaking, seems to be inversely 

 proportional to the size, but proportional to the activity, of the 

 food organisms. Food vacuoles composed entirely of surrounding 

 liquid medium have occasionally been observed. Edwards (1925) 

 observed ingestion of fluid-medium by an amoeba by forming 

 food-cups under changed chemical composition. Brug (1928) re- 

 ports seeing Entamoeba hystolytica engulf liquid culture medium 

 by formation of lip-Uke elevation of the ectoplasm and Kirby 

 (1932) figures ingestion of the brine containing no visible organ- 

 isms by the cytostome of Rhopalophrya salina. Mast and Doyle 

 (1934) stated that if Amoeba proteus, A. dubia, A. dofleini, or A. 

 radiosa is placed in an albumin solution, a hypertonic balanced 

 salt solution or a hypertonic solution of calcium gluconate, it rap- 

 idly decreases in volume, and forms numerous tubes filled with 

 fluid, which disintegrate sooner or later and release their fluid 

 content in the cytoplasm. At times 50 or more such tubes may be 

 present, which indicate that the organism ingests considerable 

 quantities of fluid in this way. The two authors consider that it is 

 "a biological adaptation which serves to compensate for the rapid 

 loss of water." The food vacuoles finally reach the endoplasm and 

 in forms such as Amoebina, the vacuoles are carried about by the 

 moving endoplasm. In the ciliates, the fluid endoplasm often 

 shows a definite rotation movement. In Paramecium, the general 

 direction is along one side up to the anterior end and down the 

 other side, with a short cyclosis in the posterior half of the body. 

 In Carchesium, according to Greenwood, the food-vacuoles pass 



