52 GENERAL ORGANIZATION OF THE PROTOZOA 



the same origin from the nucleus that the axial rays of the filose 

 pseudopodia have. Cilia, however, arise from small basal bodies 

 called microsomes, which have a nuclear origin and belong apparently 

 in the same category of kinetic stufi's as the substance of flagella. In 

 many of the infusoria these granules are arranged in definite lines or 

 rows, forming threads of contractile substance which lie immediately 

 below the cuticle. These threads, called myonemes, are in reality 

 primitive muscle elements, and their sudden contraction resembles 

 the action of the complicated muscle bundles of the metazoa 

 (Fig. 19). 



Subphylum INFUSORIA. Protozoa in which the motor apparatus is in the form 

 of ciha, either simple or united into membranes, membranelles, or cirri. The 

 cilia may be permanent or limited to the young stages. With two kinds of 

 nuclei, macronucleus and micronucleus. Reproduction is effected by simple 

 transverse division or by budding. Nutrition is holozoic or parasitic. 



Class I. CILIATA. Infusoria jDrovided with cilia during all stages. Reproduction 

 is brought about typically by simple transverse division. INIouth and anus 

 are usually present. The contractile vacuole is often connected with a com- 

 plicated canal system. 



Order 1. Holotrichida. Ciliata in which the cilia are similar and distributed all 

 over the Ijody, with, however, a tendency to lengthen in the vicinity of the 

 mouth. Trichocysts are always present, either distributed about the body 

 or limited to a special region. 



Suborder 1. Gymnostomina. Holotrichida without an undulating membrane 

 about the mouth, which remains closed except during food-taking intervals. 



Family 1. Enchelinidw. The mouth is always terminal or subterminal, and is 

 usually round or oval in outline. Food taking is usually a process of swal- 

 lowing. 



Typical genera: Holophrva, Ehr., 1831; Urotricha, Clap; and Lach., 1858; 

 Enchelys, Hill, 1752,'Ehr., 1838; Spathidium, Duj., 18-11; Chenia, Quen- 

 nerstadt, 1868; Prorodon, Ehr., 1833; Dinophrya, Biitschli, 1888; Lacry- 

 maria, Ehr., 1830; Trachelocerca, Ehr., 1833; Actinobolus, Stein, 1867; 

 Ileonema, Stokes, 1884; Plagiopogon, Stein, 1859; Coleps, Xitsch, 1827; 

 Tiarina, Bergh, 1879; Stephanopogon, Entz, 1884; Didinium, Stein, 1859; 

 Mesodinium, Stein, 1862; Biitschlia, Schuberg, 1886. 



Family 2. Trachelinida\ The body is distinctly bilateral or asymmetrical, with 

 one side, the dorsal, slightly arched. The mouth may be terminal or sub- 

 terminal, or the entire mouth region may be drawn out into a long proboscis. 

 An esophagus or gullet may or may not be present; when present, it is usually 

 supported by a specialized framework. 



Typical genera: Amphileptus, Ehr., 1830; Lionotus, Wrzesniowski, 1870; Loxo- 

 phvilum, Duj., 1841; Trachelius, Schrank, 1903; Dileptus, Duj., 1841; 

 Loxodes, Ehr!, 1830. 



Family 3. ChlamydodontidcE. The general form is oval or kidney-shaped. The 

 mouth is almost always in the posterior region. The pharynx is supported 

 by a rod-apparatus or a smooth, firm tube. 



Subfamily 1 . Nassidinw. Ciliation is complete. 



Typical genera: Nassula, Ehr., 1833. 



Subfamily 2. Chllodontinw. The body is generally flattened, and the cilia are 

 stronger on the tlorsal side, or are confined to that region. 



Typical genera: Orthodon, Gruber, 1884; Chilodon, Ehr., 1833; Chlamydodon, 

 Ehr., 1835; Opisthodon, Stein, 1859; Phascolodon, Stein, 1857; Scaphidio- 

 don. Stein, 1857. 



