PAKAMCECIUM, 59 



observe that this whole cavity is lined with cilia, and that 

 they are in active operation, producing currents in the 

 water, by which food-particles are swept into the mouth ; 

 the gullet does not lead by a continuous tube to a defi- 

 nite stomach, but any part of the body within acts as a 

 stomach. When a collection of food-particles has accu- 

 mulated at the lower end of the gullet, the mass, by a 

 contraction of the body, is forced further into the soft 

 substance of the body, leaving the blind end of the gullet 

 as it was before. By sifting some finely powdered indigo 

 into the water this process of taking food may be better 

 seen. These animals seem to have little or no sense of 

 taste, as indigestible particles are readily taken in. There 

 is a regular place for ejecting such indigestible matter; 

 watch patiently to make out where this is. 



Note the changes of shape which the body undergoes 

 as it forces its way through narrow places, between par- 

 ticles of sediment in the water. 



If a specimen that is pretty quiet be carefully watched, 

 a large transparent space will be seen at some point in the 

 body; this, after remaining visible for some twenty or thirty 

 seconds, will suddenly disappear, and gradually reappear ; 

 this is the contractile vesicle. In some species there are 

 two contractile vesicles. 



Watch closely the food-masses ; do they retain their 

 original size? Do they maintain a fixed position? 



Make a drawing showing — 



1. The shape of the body. 



2. The vestibule and gullet. 



3. The food-masses. 



4. The cilia. 



5. The contractile vesicle. 



