372 HANDBOOK OF PROTOZOOLOGY 



Plagiotoma lumhrici Dujardin (Fig. 160, a). In the intestine 

 of the common earthworm, Lumhricus terrestris. Length 130 to 

 210 microns. 



Genus Nyctotherus Leidy. Body oval or reniform, more or 

 less compressed dorso-ventrally. Body surface uniformly cili- 

 ated. Peristome begins a little back of the anterior end of the 

 body, winding slightly toward the middle of the body, and 

 forms the cytostome, from which a small cytopharynx continues 

 down. The macronucleus is oval or sausage-shaped and an- 

 teriorly located. Contractile vacuole at the posterior end, where 

 a permanent cytopyge is present. Several species. 



Nyctotherus ovalis Leidy (Fig. 160, b, c). In the colon of the 

 cockroach. Common. Body length up to 350 microns. 



Nyctotherus cordiformis Stein (Fig. 160, d, e). In the large 

 intestine of frogs and toads. Length about 165 to 240 microns. 



Genus Blepharisma Perty. Body medium large, constant in 

 form; often reddish in color. Anterior part compressed, 

 pointed, sickle-shaped, and curved toward the left. Peristome 

 deep, oblique, but straight; with an adoral zone and undulating 

 membrane at the posterior part. Cytopharynx inconspicuous, 

 curved. Striation spiral and uniform. Macronucleus elongate or 

 spherical; contractile vacuole near the posterior end. Fresh 

 water. 



Blepharisma lateritia Ehrenberg (Fig. 160, /). Body rose- 

 red due to the presence of zoopurpurin (p. 23). 50 to 150 

 microns long. Fresh water, often in infusion. 



Genus Spirostomum Ehrenberg. Body highly elastic and 

 contractile. When extended it is quite long. Cylindrical or 

 slightly flattened. Anterior end rounded, posterior end trun- 

 cate. Peristome narrow and long. Adoral zone on the left side 

 ridge; no undulating membrane. Cytostome and cytopharynx 

 small. Contractile vacuole canal-like with a large reservoir near 

 the posterior end. Uniform ciliation. Fresh or salt water. 



Spirostomum amhiguum Ehrenberg (Fig. 160, g). Cosmo- 

 politan in fresh water and infusion. Some authors distinguish 

 varieties, based chiefly upon the dimensions. Thus, Roux holds 

 that var. major is more than 2 mm. long when extended and 

 that var. minor seldom reaches 500 microns in length. Kahl 

 adds to them var. inflatum which measures 300 to 400 microns 



