(contains many sets of chromosomes). It may 

 be single (compact, ribbonlike, beaded, or 

 branched) or separated into membrane-bound 

 structures that typically reconsolidate prior to 

 fission. Macronuclei of members of the Trache- 

 locercidae, Loxodidae, and Geleiidae have exten- 

 sive Feulgen-negative areas, cannot replicate, 

 and, in some cases, have been shown to be diploid. 



Within the Ciliophora there is wide variation 

 in the arrangement of the cilia, and this forms 

 the basis for classification. Cilia are absent at 

 some stages of the life cycle of all members of 

 the order Suctorida, many members of the 

 family Sphenophryidae, and members of the 

 genus Conidiophrys. Cilia may occur singly, 

 in rows, bands, or ribbons, or may be grouped 

 as compound structures (cirri, undulating mem- 

 branes, and membranelles). Ciliates that lack 

 cilia during much of their life cycle, however, 

 possess other characteristics of the group. 



Except for members of the Suctorida, Asto- 

 matida, and some members of the order Thig- 

 motrichida, all ciliates possess a permanent open- 

 ing, the cytostome, through which food is 

 ingested. 



All ciliates are heterotrophic and do not ex- 

 hibit ameboid locomotion. In binary fission, the 

 division plane bisects the ciliary rows, dividing 

 the cell into anterior and posterior daughter 

 cells. 



GLOSSARY 



The following terms are used in this key to 

 describe the anatomy of marine ciliates. Com- 

 monly used terms are illu.strated in Figures 1-5. 

 More complete definitions of structures are given 

 by Corliss (1959). 



Ahoral Surface opposite that on which the 

 cytostome or buccal cavity occurs. 



Buccal cavity A depression in the surface of 

 the cell containing cilia that are differentiated 

 from those of the general body surface and 

 that are used in feeding. This cavity contains 

 the cell mouth or cytostome (see Fig. 1). 



Buccal cilia Cilia in the buccal cavity used in 

 feeding. These cilia usually are organized 

 into compound organelles, such as an undulat- 

 ing membrane or membranelles. 



Cilianj row A linear series, usually longitudi- 

 nal, of simple cilia (see Fig. 2, 3). 



Cirrus A compound ciliary organelle polygonal 

 in cross section, composed of several to dozens 

 of individual cilia. These usually occur on the 

 ventral surface of members of the order Hy- 

 potrichida and are used in locomotion (see 

 Fig. 1). 



Compound ciliary organelle Any structure such 

 as a cirrus, undulating membrane or membra- 

 nelle composed of many functionally united 

 cilia. 



Contractile vacuole A clear membrane-bound 

 vesicle functioning in expulsion of water and 

 accompanied by rhythmic changes in its di- 

 ameter. 



Cytopharyngeal rod Stiff fibrous structures 

 lining the cytopharynx, often in a conical ar- 

 rangement (see Fig. 3). 



Cytopha)-ynx That part of the c\i;oplasm im- 

 mediately adjacent and internal to the cyto- 

 stome and not ciliated (see Fig. 3). 



Cytostome The cell mouth. This may be on 

 the surface, in a vestibulum ciliated by the 

 cilia of the general cell surface, or in a buccal 

 cavity (see Fig. 5). 



Front o-ventral cirri Cirri arranged in scat- 

 tered groups anterior to the transverse cirri. 



Lorica A secreted chamber open at least at one 

 end in which some ciliates live. 



Marginal cirri Cirri arranged in longitudinal 

 rows to the right and left of the ventral mid- 

 line (see Fig. 1). 



Memhranelle A compound ciliary organelle! 

 composed of several closely set and parallel 

 rows of cilia. They are associated with a buc- 

 cal cavity and may function both in feeding 

 and in locomotion (see Fig. 1). 



Motile Capable of independent locomotion on 

 or oflF the substratum. 



Penicuhis A comjiound ciliary organelle of the 

 buccal cavity of some members of the order 

 Hymenostomatida. It may consist of a band 

 typically four cilia wide but many cilia in 

 length, very compactly arranged (see Fig. 4). 



Psammolittoral Living in interstices among 

 sand grains. 



Scopida A surface organelle that secretes the 

 stalk in many sessile ciliates. Usually at one 

 apex of the cell. 



Sessile Generally incapable of locomotion. 

 Usually attached to a substratum by a stalk or 

 flattened sole, or wrapped around the bristle 

 of some invertebrate. 



