266 PARAMCECIUM CHAP. 



spindle-shaped spaces filled with fluid appear round it, like 

 the rays of a star (upper vacuole in A & 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 & 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 dis- 

 charged to the exterior. 



The process of feeding can be very conveniently studied 

 in Paramcecium 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 neigh- 

 bourhood 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 con- 

 traction 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 Paramcecium there are to be seen numerous 

 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 pro- 

 toplasm also takes place in a definite direction, and thus a 

 circulation of food-vacuoles is produced, as indicated in 

 Fig, 71, B, by arrows. 



