86 DAVENPORT ACADEMY OF SCIENCES. 



Paramecium bursaria Ehr. 



Body elongated, nearly twice as long as broad, rounded poster- 

 iorly, the anterior border obliquely truncate. Oral groove broad, 

 extending backward beyond the center of the body and terminat- 

 ing in the mouth. Nucleus central. Contractile vesicles two in 

 number, one in either extremity. Endoplasm usually colored 

 green. 



Length, 120 microns. (Fig. 139, PI. XVIII.) 



Normally the endoplasm of this species is crowded with green 

 chromatophores, the chlorophyl -bearing granules near the per- 

 iphery being elongated and in their appearance are not unlike a 

 layer of columnar epithelium. 



This peripheral layer is quite permanent in position, not being 

 shifted about by the powerful endoplasmic current which is even 

 more noticeable than in Paramcccium caudahim. The green color- 

 ing matter is probably a mark of age, as apparently immature 

 individuals have been observed almost devoid of chlorophyl. 



Paramcecium bursaria is a sluggish organism, not very irritable, 

 seldom turning on its longitudinal axis but gliding along, when 

 in motion, with the ventral surface down. 



Trichocysts are well developed. 



Reproduction is by transverse fission. 



This species, although not a common one in this state, may be 

 found among algae in fresh water.. Mostly solitary. 



ParamtECium trichium Stokes. 



Body oval, both extremities rounded, slightly flattened ven- 

 trally. Oral groove broad anteriorly, extending obliquely back- 

 ward to the center of the body, ending in an oral aperture which 

 leads into a ciliated pharynx. Nucleus oval, centrally located. 

 Contractile vesicles two, close together in the anterior extremity 

 of the body. Trichocysts abundant. Endoplasm transparent. 



I,ength, 75-100 microns. (Fig. 140, PI. XVIII.) 



Found in stagnant infusions of pond water, usually appearing in 

 the bacteria-laden film at the surface. 



Reproduction is by transverse fission. 



Conjugation has often been observed to take place as in Para- 

 mcBcium catidatuni. 



