156 



BIOLOGY OF THE PROTOZOA 



is usually differentiated into a specialized food-collecting, frequently 

 funnel-like structure called the peristome. Cilia on the floor of the 

 peristome are usually longer than in other parts of the body, and in 



I I 



mm 



' * J : 





Fig. 85.— Types of Lacrymaria. A, Lacrymaria sp.; 5, and C, retracted and ex- 

 panded phases of Lacrymaria olor; D, Lacrymaria lagenula. (After Calkins.) 



four of the five orders of ciliates some of these are invariably aggre- 

 gated in triangular, quadrilateral or ribbon-like membranelles and 

 membranes for producing food-bringing currents of water toward 



