Feb., 1920] The Protozoa of Mirror Lake 115 



Ophryoglena atra Ehrenberg. 



This species was common among alga-covered poplar roots 

 (Station D) on January 7. 

 Length 144/i. 



Colpidium colpoda (Ehrenberg). 



This form was abundant during January and February in 

 algae at Station G; during March it was common in sediment 

 from the stone near the outlet of the larger pond (Station K) . 



Length 90-1 12^. 



Loxocephalus granulosus Kent. 



This animal was abundant late in October in algae taken 

 from Station E. There were two adcurved setae near the 

 anterior end of the cell. In this and other respects, the speci- 

 mens seen agreed with the description and drawing of Kent 

 (1881). The ring of larger cilia figured and described by Biitschli 

 (1883-88) was not seen. 



Length SO^u; breadth loAt. 



Colpoda sp.? PI. Ill, Figs 2 and 2a. 



This organism was found in algae from a submerged stone 

 at Station G on December 3. An attempt to place it in 

 described species failed. The cell is broadly oval, slightly 

 tapering at the anterior end and covered by numerous fine cilia 

 arranged in rows. A gullet lined with cilia occupies a position 

 a short distance from the anterior end. The meganucleus is 

 large, rounded and situated posterior to the gullet. The 

 micronucleus lies in contact with the meganucleus; both these 

 bodies were plainly visible even in the unstained specimen. A, 

 large contractile vacuole occupies the posterior part of the cell. 



Length 89iu; breadth 74/i. 



Family Urocentridoe. 



Urocentrum turbo (Miiller). PI. Ill, Fig. 6. 



This species was abundant during October in sediment 

 drained from the leaves at Station A, and in the black sediment 

 of Station B close by. In November it was common in floating 

 algae from Station C ; in February it was common only on alga- 

 covered poplar roots (Station D). Several pairs of individuals 

 taken in February presented the appearance shown in outline 



