56 PEOTOZOA 



PARAMECIUM* 0. F. Miiller. Slipper-animalcules. Characters as 

 above; trichocysts distinct; two contractile vacuoles: 4 species; in fresh 

 and salt water. 



P. aurelia Mill. (Fig. 91). Forward end rounded; hinder end bluntly 

 pointed; length .15 mm.; 2 micronnclei: in fresh and salt water; common. 



P. caudatum Ehrenberg (Fig. 92). Like P. aurelia, but somewhat 

 larger and more pointed behind and with 1 micronucleus : in fresh 

 water; commoner than the preceding. 



Fig. 90 Fig. 91 Fig. 92 



\trum turlo (Conn). Fig. 91 and Fig. 92 Pan 

 and P. caudatum in outline (George T. Hargitt). 



Fig. 90 Urocentrum turbo (Conn). Fig. 91 and Fig. 92 Paramecium aurelia 



utlin 



P. bursaria Ehr. Body wide, rounded, and obliquely truncate for- 

 ward and pointed or rounded behind; usually bright green from the 

 numerous green algae (zoochlorellae) in the ectosarc; length .12 mm.: 

 in fresh water. 



FAMILY 7. PLEURONEMIDAE. 



Body oval or ellipsoidal, with a long, deep oral groove leading to 

 the mouth in hinder part of body; along the edge of this groove is a 

 large undulating membrane: 5 genera. 



Key to the genera of Pleuronemidae here described : 



Oj No caudal bristle. 



&! Hinder end acute 1. LEMBADION 



6 2 Hinder end rounded 2. PLEURONEMA 



o 2 Caudal bristle present 3. LEMBUS 



1. LEMBADION Perty. Body oval, rigid, posterior end acute: 1 

 species. 



L. bullinum Perty (Fig. 93). Length .05 mm.: in fresh water. 



2. PLEURONEMA Dujardin. Body rigid, oval, and flattened; oral 

 groove takes in a large part of the ventral surface and with a high, undu- 

 lating membrane ; cilia very long : 2 species ; in fresh and salt water. 



P. chrysalis (Ehrenberg) (Fig. 94). Moves by springs and by swim- 

 ming; length .04 mm.: in fresh and salt water; in decaying vegetation. 



* See "Races of Paramecium," by H. S. Jennings and G. T. Hargitt, Jour. Morph., 

 Vol. 21, p. 495, 1910. "Two Thousand Generations of Paramsecium," by L. L. 

 Woodruff, Arch. f. Prot. Vol. 21, p. 263, 1911. "Paramaecium aurelia and P. 

 caudatum," by same, Jour. Morph., Vol. 22, 1911. 



