54 GENERAL ORGANIZATION OF THE PROTOZOA 



Suborder 1. POLYTRICHIXA. Heterotrichous ciliates provided with a uniform 

 coating of cilia. 



Family 1. Plagiotomidos. The peristome is a narrow furrow, which begins, as a 

 rule, close to the anterior end, and runs backward along the ventral side to the 

 mouth, which is usually placed between the middle of the body and the pos- 

 terior end. A well-developed adoral zone stretches along the left side of the 

 peristome, and it is usually straight. 



Typical genera: Conchophthirus, Stein, 1861; Plagiotoma, Duj., 1841; Nycto- 

 therus, Leidy, 1849, a subgenus; Blepharisma, Perty, 1849; Metopus, Clap, 

 and Lach., 1858; Spirostomum, Ehr., 1835. 



Family 2. Bursaridce. The body is usually short and pocket-like, but may be 

 elongate. The chief characteristic is the peristome, which is not a furrow, 

 but a broad triangular area, deeply insunk, and ending in a point at the 

 mouth. The adoral zone is usually confined to the left peristome edge, or it 

 may cross over to the right anterior edge. 



Typical genera: Balantidium, Stein, 1867; Balantidiopsis, Biitschli, 1888; Con- 

 dylostoma, Duj., 1841; Bursaria, O. F. Miiller, 1773; Thylakidium, Sche- 

 wiakoff, 1892. 



Family 3. Stentoridcc. The peristome is relatively short and limited to the front 

 end of the animal, so that its plane is nearly at right angles to that of the 

 longitudinal axis of the body. The adoral zone of cilia either passes entirely 

 around the peristome edge, or ends at the right-hand edge. The surface of the 

 peristome is spirally striated and provided with cilia. Undulating membranes 

 are absent. 



Typical genera: Climacostomum, Stein, 1859; Stgntpr, Oken, 1815; Folliculina, 

 Lamarck, 1816. Genera incrrttr si'di.v: Cenomorpha (Gyrocorys, Stein), 

 Perty, 1852; Maryna, Gruber, 187'.). 



Suborder 2. OLIGOTRICHIXA. Heterotrichous ciliates characterized by the reduced 

 cilia, which are limited to certain localized areas. 



Family 1. lAeberkuhnidoe. This name was given by Biitschli for certain little- 

 known forms, which were at first considered young Stentors. 



Family 2. Haltcriidw. The peristome has no cilia, and only a few scattered ones 

 can be found on the ventral and dorsal surfaces. 



Typical genera: Strombidium, Clap, and Lach., 1S5S; llaltcria, Duj., 1N41. 



Family 3. Tintinnidae. The body is attached by a stalk tolTtheca. Inside of the 

 adoral zone of membranelles is a ring of cilia (paroral cilia ). 



Typical genera: Tintinnus, Fol., 1889; Tintinnidium, Kent, 1881; Tintinnopsis, 

 Stein, 1867; Codonella, Haeckel, 1873; Dictyocysta, Ehr., 1854. 



Family 4. Ophryoscolecidce. Heterotrichous ciliates characterized by a thick 

 cuticle and deep funnel-like peristome. The posterior end is provided with 

 distinct spine-like processes, while the terminal anus is provided with a well- 

 defined anal tube. 



Typical genera: Ophryoscolex, Stein, 1859; Entodinium, Stein, 1859; Diplo- 

 dinium, Schuberg, 1888. 



Order 3. Hypotrichida. Ciliata in which the cilia are limited to the ventral surface 

 of a dorsoventrally flattened body; they are frequently fused to form larger 

 appendages, the cirri, and an adoral zone of membranelles. The dorsal sur- 

 face is frequently provided with bristles. A pharynx may be absent or but 

 slightly developed. 



Family 1. PeritromidcF. The peristome is but slightly marked off from the 

 remaining frontal area. The cilia on the ventral surface are uniform in size 

 and arrangement, and are not differentiated into cirri. 



Typical genera: Peritromus, Stein, 1862. 



Family 2. Oxyirichida'. The peristome is not always distinctly marked off from 

 the frontal area. In the most primitive forms the ciliation on the ventral sur- 



