THE ROTATORIA OF THE LAKE OKOBOJI REGION* 
DWIGHT C. ENSIGN 
INTRODUCTION 
This report is based upon a series of collections and studies 
made during the months of July and August, 1919, at the Iowa 
Lakeside Laboratory. It is incomplete, since numerous species 
which will doubtless be found in this locality have been missed by 
reason of the short time during which collections were made. 
The region of the Iowa Lakeside Laboratory seems to be an 
especially good place for the study of the Rotatoria. A wide variety 
of habitats is within available distance of the laboratory grounds ; 
the Open lake, the quieter waters of the sand-bar pond and the 
canal, the numerous kettle holes, and the marshy swamps near 
the lake shore afford many different kinds of collecting. It is 
probable that succeeding years of study will as much as double 
the list of species found in this locality this year, one hundred 
and eight in all, of which five have not yet been satisfactorily iden- 
tified and are not included in this report. 
Little work has been done upon the Rotatoria of the state of 
Iowa, so that it is difficult to know how many forms to expect. The 
only other list of Iowa rotifers which was available for com- 
parison was one prepared by Mr. Wright Stacy ^ of the State 
University of Iowa; twenty-eight species were listed, all except 
five of which were found at Okoboji also. The species recorded 
from Iowa City by Mr. Stacy which did not appear in this 
summer’s collections are: Brachionus urceus (Linnaeus), Mono- 
styla arcuata (Bryce), Lepadella oblongata (Ehrenberg), Diurella 
weberi (Jennings), and Philodina erythopthalma (Ehrenberg). 
It might be mentioned in passing that Mr. Stacy’s Brachionus 
urceus ^ would seem from his figure to be the Brachionus urceo- 
laris of Hudson and Gosse,^ which by Harring, in his Synopsis of 
the Rotatoria ^ is assigned to Brachionus capsuMorus, a species 
which occurred in great abundance at Okoboji. 
* Based upon collections and studies made during the summer of 1919 at The Iowa 
Lakeside Laboratory. 
1 Stacy, Wright, Studies of the Rotifera of Iowa — A Thesis. 
2 Idem., p. 42, plate V, figure 2. 
3 Hudson and Gosse, The Rotifera, volume II, p. 118, plate XXVII, figure 6. 
4 Harring, H. K., Synopsis of the Rotatoria: U. S. Natl. Museum Bull. 81, p. 20. 
