284 



THE PROTOZOA 



considerable quantity of water accompanies the food particles, what- 

 ever they might be, into the protoplasm, and forms the fluid of the 

 gastric vacuole, and later physiologists Ijave found that this water be- 

 comes acid by gradual secretion from the surrounding protoplasm. 

 (Fabre-Dumergue, Meissner, Metschnikoff, '89; Le Dantec, 'go). 1 

 It thus appears, if these observations be complete,, that in these cases 

 at least the food particles never come in direct contact with the pro- 



B C D E 



Fig. 146. Digestion in Reticulariida. [VERWORN.] 



A, B, C, D, E, successive stages in the disintegration of a ciliate (Colpoda) (c), in a pseudo- 

 podium of Lieberkiihnia. 



toplasm, but are always suspended in the liquid of the vacuole. 

 There are, however, certain exceptions to this rule, and with 

 these in mind, it is not yet possible to regard the subject as 

 definitely established. Food-taking in certain marine Rhizopoda 

 is apparently accomplished without the formation of a gastric vacuole, 

 and the prey, possibly a small ciliate, disintegrates while in contact 

 with the plasm, and the disintegrated parts move about in cyclosis 

 with the endoplasmic granules (Lieberkiihnia, Gromia fluiriatilis, 

 Fig. 146). In these cases the digestive fluids must be in any and all 

 1 Cf., however, Greenwood ('94). 



