382 LAKES AND STREAMS 



like covering. Equally interesting are the flagellated infusorians, one species of 

 which, Euglena vlrldis, is occasionally found in such numbers as to give the 



water the appearance of green-pea 

 soup. When at rest it is spindle- 

 shaped, and has a red speck at one 

 end. Another common species is 

 Volvox globator, a spherical colony 

 of single cells, which moves forward 

 in the water with a rolling motion. 

 Among the group of Heliozoa is the 

 sun-animalcule (Actinophrys sol), 

 which is a globular mass of tissue 

 with radiating thread-like processes. 



Lastly, the group of Lobosa is 

 represented by Amoeba proteus, 

 found on the muddy bottoms of 

 ponds, which is about -j^ inch in 

 diameter and constantly changes in 

 volvox. shape, gliding along by protruding 



and retracting its thread-like pro- 

 cesses or pseudopods, and occasionally swimming as a mere mass of jelly, recognis- 

 able only by its nucleus. Another species, A. prinre[>s, lias several of these fixed 



THE SUN-ANIMAL' TLE. 



points or nuclei. Rather more definite is Pdomyxa palustris, a white egg-shaped 

 sac, about the size of a pin's head, which glides over the mud of stagnant pools, 

 broad end foremost. 



