FRESH-WATER POLYZOA. 243 



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

 phophore close together, the tentacles collect them- 

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

 drawn back into the Dody, a muscle around the border 

 closing 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 encloses the lophophore and tentacles, which are 

 thus doubly protected. When the danger is past, the 

 tips of the bundle of tentacles are cautiously pushed 

 out into the water, the lophophore follows, and if the 

 creature's confidence is restored, the crowns are 

 spread open in all their indescribable grace and 

 beauty. 



The favorite food consists of small Algse and Infuso- 

 ria, which the ciliary currents sweep toward the mouth, 

 the tentacles "forming a cage from which the most act- 

 ive little animals seldom escape unless the captor is 

 willing. And not only are the tentacles used to cap- 

 ture the food, but "for a multitude of other ofifices. 

 They are each capable of independent motion, and 

 may be twisted or turned in any direction; bending in- 

 ward, they take up and discard objectionable matter, 

 or push down into the stomach and clear the oesopha- 

 gus of food too small to be acted on by the parietal 

 muscles. " 



To examine the Polyzoa under the microscope de- 

 mands a deep cell to hold a large quantity of water and 

 to prevent the cover-glass frbm pressing on the bodies. 

 It is often better to place the microscope in an up- 

 right position and to omit the thin cover. In this ar- 

 rangement the water trembles easily, and not only in- 

 terferes with the distinctness of the image, but terri- 



