IOWA ACADEMY OP SCIENCE 
171 
Rather rare in old cultures in which Euglena and Amoeba were beginning to 
appear. The green coloring matter of this species is due, according to European 
algologists, to the presence within the animalcule of numerous individuals of a 
Protococcoid Alga, GTilorella vulgaris Beyer, and not to a pigment of the ParOr 
maecium itself. So far as I was personally able to study the form this view 
of a duality of species appears to be the correct one. 
24. Paramaecium trichinum Stokes. 
Rare among the bacteria in an old culture of pond water. 
Family Stentoridae. 
25. Stentor caeruleus Ehr. 
Common in old cultures after the bacteria had disappeared, and frequently 
in company with Amoeba proteus. 
Family Oxtrichidae. 
26. OXTHRICHIA PELUONEIXA Muehl. 
Common in old cultures of both pond and spring water. 
27. Stylonychia mytilus Ehr. 
Very common in old cultures from which Paramaecium caudatum had almost 
disappeared. 
28. Stylonychia pustulata Ehr. 
Common, in similar cultures to the last, but not always associated with that 
species. 
Family Vorticellidae. 
29. VORTICEELA CAMPANULA Ehr. 
Very common in colonies in pond water, especially from ponds where there 
was an abundance of semi-decaying vegetation. 
30. VORTICELLA NUTANS Mull. 
Rather rare in pond water. 
31. VORTICELLA ALBA From. 
Rather rare in pond water. 
32. VORTICELLA L0N6IFILUM SK. 
A solitary form which is rather common in pond water. 
33. Bpistylis flavigans Ehr. 
Rare in cultures from which Yorticella had disappeared. 
