80 THE AMEKICAN MONTHLY [April, 



Fresh-water Rhizopods of Oakland County, Michigan. 



By STUART H. PERRY, 



ANN ARBOR, MICH. 



The list of species given in this papei" is the result of about two 

 years' study of the Rhizopoda of Oakland county. The localities I 

 have searched are the usual habitats of the Rhizopoda, including the 

 numerous lakes, ponds, and streams in the vicinity of Pontiac, for 

 sphagnum moss and the stems and leaves of aquatic plants. In gen- 

 eral I have found sphagnum when growing in shady situations to be 

 most productive, although the largest variety I ever observed in a single 

 gathering was from Clinton river, among the fine, thread-like roots of 

 tlie willow. I find the habits substantially as described by Prof. Leidy 

 in his work on the Rhizopods of the United States, which has been my 

 chief authority in classifying the following list: 



Pseudodiflflugia gracilis. 



Englypha olveolata. 

 " ciliata. 

 " cristata. 



Cyphoderia ampulla. 



Centropyxis aculeata. 



Campascus cornutus. 



Trinema enchelys. 



Clathrulina elegans. 



Vampyrella lateritia. 



Hyalosphenia elegans. 



Actinosphaerium eichornii. 



Actinophrys sol. 



Acanthocystis. 



Heterophrys. 



Radiophrys. 

 Of these species I found Nos. i , 5, 6, 7, 8 common ; 3, 4, 16, 17, 27 

 rare; 2, 9, 10, 11, 12, 14, 18, 21, 28 rather common; 13, 22, 29 very 

 common; 15, 19, 20, 30, 31, 32 occasional; 23 a single specimen ob- 

 served. This species was first described by Leidy, and found by him 

 only in China lake, Yinta Mts., Wyoming ; '24 common in sphagnum ; 

 25 not common ; 26, I found this very abundant with Oidogonium in 

 a bottle in my laboratory. 



If possible Rhizopods should be examined and studied while alive, 

 but the testaceous forms may be mounted so as to show very well many 

 of their characteristics. I find the best medium for mounting to be 

 glycerine jelly, in which the specimens do not become too transparent 

 as they would in balsam, and the sarcode is preserved, though of course 

 somewhat contracted. As fresh-water rhizopods are seldom sufficiently 

 plentiful to warrant the treatment by levigation which facilitates the 

 separation of Foraminifei-a and Diatoms, it is usually best to pick 

 them out singly with a fine camel's-hair brush under a power of from 

 25 to 125 diameters, transferring them to a drop of glycerine, where 

 they may remain indefinitely until required for mounting. When a 

 single species is very abundant, however, time may be saved by care- 

 fully washing the material and finally isolating the specimens as de- 

 scribed. 



Pontiac, Mich. 



