266 PARAMCECIUM CHAP. 



six to ten of delicate, radiating, spindle-shaped spaces 

 filled with fluid appear round it, like the rays of a star 

 (upper vacuole in A and B) : the vacuole itself contracts 

 or performs its systole, completely disappearing from 

 view, and immediately afterwards the radiating canals 

 flow together and refill it, becoming themselves emptied 

 and therefore invisible for an instant (lower vacuole 

 in A and B) but rapidly appearing once more. There 

 seems to be no doubt that the water taken in with the 

 food is collected into these canals, emptied into the 

 vacuole, and finally discharged to the exterior. 



The process of feeding can be very conveniently 

 studied in Paramoecium by placing in the water 

 some finely-divided carmine or indigo. When the 

 creature comes into the neighbourhood of the coloured 

 particles, the latter are swept about in various directions 

 by the action of the cilia : some of them, however, are 

 certain to be swept into the neighbourhood of the buccal 

 groove and gullet, the cilia of which' all work downwards, 

 i.e., towards the inner end of the gullet. The grains of 

 carmine are thus carried into the gullet, where for an 

 instant they lie surrounded by the water of which it is 

 full : then, instantaneously, probably by the contraction 

 of the tube itself, the animalcule performs a sort of gulp 

 and the grains with an enveloping globule of water or 

 food-vacuole are forced into the medullary protoplasm. 

 This process is repeated again and again, so that in any 

 well-nourished Paramoecium there are to be seen numer- 

 ous globular spaces filled with water and containing 

 particles of food or in the present instance of carmine 

 or indigo. At every gulp the newly-formed food-vacuole 

 pushes, as it were, its predecessor before it : contraction 

 of the medullary protoplasm also takes place in a definite 

 direction, and thus a circulation of food-vacuoles is 

 produced, as indicated in Fig. 71, B, by arrows. 



