148 



BIOLOGY OF THE PROTOZOA 



In some types the anterior membranelles fold over the peristome 

 forming an opercuhim as in Uronychia setigera (Fig. 107, p. 225). 



Fig. 76. — Types of Lacrymaria. A, Lncrymaria sp.: B, and C, retracted and expanded 

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



While in most cases the membranelles represent the fusion of 

 comparatively few cilia in transverse rows of the peristome, making 

 them relatively narrow at the base, in other cases, notably in the 

 Tintinnidse, such fnsion includes practically all of the cilia of the 



