Plankton Studies II On Pleodorina illinoiensis, A New Species from the Plankton of the Illinois River

The genus Pleodorina was discovered in 1893 by Shaw ('94) at Palo Alto, California, and in May of the following year the species Pleodorina californica, upon which the genus was founded, was detected by Mottier ('94) in water from a shallow stagnant pool near Bloomington, Indiana. During the same summer the form also occurred in the Illinois River and its adjacent waters (Clinton, '94), and it has been found in the plankton of these situations in succeeding years from Tune to September. The distribution of the species in this continent is thus quite extended, and it is not at all improbable that continued investigation of fresh-water plankton will demonstrate that this genus has a cosmopolitan distribution similar to that of some other genera of the family Volvocineae to which it belongs.Ope