Feb., 1920] The Protozoa of Mirror Lake 99 



SYSTEMATIC REVIEW OF THE SPECIES TAKEN. 



Class Sarcodina. 



SUBCLASS RHIZOPODA. 



Order Amoebida. 



Family Amoebidce. 



Amoeba Umax Dujardin (?) 



Throughout the period of study this form was abundant 

 among the algae growing on the sides of the bowl of the spring 

 (Station J), and on the sand at the point where the spring water 

 enters the larger pond (Station E). The writer was unable to 

 see, even with the aid of a 1.8 mm. oil immersion lens, the 

 radiating fringe of delicate substance at the posterior end of the 

 animal which Penard regards as distinctive of the species. 

 The measurements given by Cash (1905) are 50-60/i; Penard 

 gives the maximum length as SOju. The animals taken in 

 Mirror Lake varied in length from 29-80/x. 



Material collected on March 22 contained an abundance of 

 amebae of the Umax form; five days later the same material 

 showed only amebae with numerous short radiating pseudopodia 

 and these were about as abundant as the Umax form had been. 

 Max Verworn (1896) has shown that by the use of appropriate 

 chemicals, Amoeba Umax may be made to assume a proteus 

 form and then a radiosa form. Doflein (1907) obtained similar 

 form changes in Amoeba vesperUUo, and showed that the body 

 form and character of the pseudopodia were quite inadequate 

 features for distinguishing the species of Amoeba, depending 

 as they do upon the conditions of the environment and the 

 nature of the medium. The writer's observation might there- 

 fore indicate, although the evidence is by no means conclusive, 

 that the Amoeba Umax discussed above and the Amoeba radiosa 

 named below may be different phases of the same species. 



Amoeba proteus (Pallas). 



This animal was present only in a very few collections made 

 late in November and early in December. It was taken in 

 algae from submerged rocks at Stations E and G. 



Diameter 119-193iu. 



