EDMONDSON — PROTOZOA OF IOWA. 39 



PHACUS Dujardin. 



Body flattened, leaf-like, with a tail-like posterior prolongation. 

 Oral opening distinct. Flagelluni single, eye-sjiot present. Color 

 usually green. 



Phacus pleuronectes Miill. 



Bod}^ flattened, oval in outline with a short posterior tail-like 

 projection, usually curved. Surface longitudinally striated. 

 Endoplasm bright green enclosing one or more large circular 

 amylaceous bodies. Nucleus often concealed, contractile vesicle 

 and pigment spot near the base of the flagelluni, which arises 

 from the cleft-like oral aperture on the anterior border. 



Length, 25-75 microns. (Fig. 55, PL VIII.) 



This species is widely distributed, being found in great abund- 

 ance in fresh water among aquatic plants, also often developed 

 in infusions of pond water. 



There are apparently several varieties of the species found in 

 this state. Fig. 55, PI. VIII, illustrates a large variety of this 

 species. Associated with this variety is sometimes found a smaller 

 form possessing two lateral amylaceous bodies, with a deep depres- 

 sion extending from the oral aperture in a median line nearly to 

 the posterior border. This may represent an immature phase of 

 Phacus picuroncctcs. A yet smaller form has been observed, the 

 endoplasm of which has a decidedl}' bluish appearance. It is not 

 improbable that this form also is a phase of Phacus picuroncctcs. 



Phacus longicaudus Ehr. 



Body rounded, flattened, produced posteriorly into a long 

 tapering, tail-like prolongation, usually straight. Endoplasm 

 green, enclosing amylaceous bodies. Surface longitudinalh' stri- 

 ated. 



I^ength, including tail, 100 microns. (Fig. 56, PI. VIII.) 



Phacus longicaudtis is recognized by its large size and long caudal 

 projection which may exceed in length half the diameter of the 

 body. Often the posterior half of the organism is twisted on its 

 longitudinal axis giving the striations of the surface an oblique 

 appearance. 



The body may become elongated to nearly twice its usual length 

 although, due to the hardness and consistency of the cuticle, the 



