Feb., 1920] The Protozoa of Mirror Lake 121 



Oxytricha pellionella Miiller. 



At the entrance of the spring into the larger pond, one 

 individual of this species was taken on the last of October. 

 Several were taken in the middle of December among algae 

 from a stone (Station G). 



Length 80ju; breadth 16)u. 



Oxytricha platystoma (Ehrenberg). 



This form was abundant in a three months old culture of 

 floating Spirogyra taken at Station C on the last day of October. 



Length 80-128^. 



Stylonychia mytilus (Miiller). 



This species was common throughout the period of study 

 in floating algae at Station C, in algae scraped from the rocks 

 at Station E, and on the alga-covered poplar roots from Station 

 D. Frequently the organisms were brightly colored, because 

 of the presence of diatoms and algae. 



Greatest length 192ju; breadth 112/i. 



— ? PI. Ill, Figs 9 and 9a. 



This form was found on November 21 on alga-covered 

 poplar roots at Station D. It is a hypotrichous ciliate and 

 differs from the ^enus Histrio in that it lacks frontal and anal 

 styles and the nuclear material is differently disposed. The 

 animal is orbicular, obliquely truncate at the anterior and 

 posterior ends, and persistent in shape. The anterior end bears 

 an uninterrupted projecting fringe of large marginal cilia, 

 which in a similar form extended along the reflected border of 

 the peristome nearly to the posterior end. Five scattered ventral 

 styles were present. Staining revealed one meganucleus, some- 

 what crescent-shaped and centrally located, and two very much 

 smaller micronuclei of spherical form and situated to one side 

 of the meganucleus. Another individual, with a greater 

 number of ventral styles was taken a few days later. This 

 observation leads the writer to suspect that the animals were 

 developmental stages, perhaps of some well-known hypotrich. 



Length 74/i. 



