FRESH -WATER POLYZOA. 227 



escape of the food. Extending from the mouth to the 

 stomach is the food passage or oesophagus, the stomach 

 itself being a widened tube, usually conspicuous on ac- 

 count of its contents and the alternate narrow, reddish- 

 brown and yellow bands traversing it lengthwise. It is 

 suspended in the hollow body, and is bathed by a color- 

 less fluid which fills the cavity and extends also into the 

 hollow tentacles. The stomach is followed by the tubu- 

 lar intestine, which curves forward, and generally opens 

 below and on the outside of the lophophore. The ani- 

 mals have no heart and no blood, unless the liquid in 

 the space between the outer walls of the stomach and 

 the walls of the body can be said to be blood. 



When the animal is frightened, the sides of the lo- 

 phophore close together, the tentacles collect themselves 

 into a bundle, and the front of the Polyzoon is drawn 

 back into the body, and a muscle around the border 

 closes that opening. The jelly of Pectinatella and the 

 hardened tubes of the other forms are, therefore, the 

 protectors of the body, while the body receives and en- 

 closes the lophophore and tentacles, which are thus 

 doubly protected. When the danger is past, the tips of 

 the bundle of tentacles are very cautiously pushed out 

 into the water, the lophophore follows, and if the creat- 

 ure's confidence is restored, the crowns are spread open 

 in all their indescribable grace and beauty. 



The favorite food consists of small Algae and Infuso- 

 ria, which the ciliary currents sweep towards the mouth, 

 the tentacles forming a cage from which the little ani- 

 11 



