Tat. 
in five instances. On the pulse of July 26, 1898, a female with four 
male eggs was found. 
This species was not reported by Apstein (’96) from the lakes 
of Holstein, but was found by Lauterborn (’98a) in the Rhine and 
its backwaters. Here also it was a summer form, appearing about 
the middle of June, with a maximum in August or September and 
disappearing late in October, conditions of distribution much re- 
sembling those in the Illinois. It is regarded, along with other 
summer forms, as monocyclic. The appearance in our waters of 
male eggs July 26, at the height of the first pulse, leads to the in- 
ference that there may be several cycles; for example, three in 
1898, with the recurrent pulses, in a single summer season. Weber 
(798) gives it as a summer rotifer in Switzerland, and Skorikow (’97) 
finds it in July-September in the Udy River,in Russia; but it is not 
reported from the Oder by Zimmer (’99), nor from the Elbe by 
Schorler (’00). Kellicott (’97) finds it in Lake Erie in small 
numbers in the summer. 
In addition to the species of rotifers noticed above, Hempel (’99) 
has reported the following in the Illinois River or its backwaters: 
Floscularia ornata Ehrbg., Lamnzas ceratophylla Schrank, Cephalosi- 
phon lamnias Ehrbg., Gctstes tntermedius Davis, O. mucicola Kell., 
Pedetes saltator Gosse, Furcularia forficula Ehrbg., F. longtseta 
Ehrbg., Eosphora aurita Ehrbg., Diglena grandis Ehrbg., D. catellina 
Ehrbg., D. biraphis Gosse, Celopus tenuior Gosse, Scaridium longi- 
caudum Ehrbg., Distyla gissensts Eckstein, D. ohtoensis Herrick, 
D. stokesi Pell, and D. hornemanni Ehrbg. 
(GNIS AP IR) EIR IC BLN 
Chetonotus sp. occurred singly in the plankton August 29, 1896, 
July 30, 1897, and February 15, 1898, with a temperature range of 
S225. tO o4-. 
ENTOMOSTRACA. 
Average number, 47,042. In 1897, a more stable year, 91,050; 
in 1896, a year of disturbed hydrograph, 50,158; in 1895, in more 
stable conditions, 148,348. The Enutomostraca appear in every collec- 
tion at all seasons of the year. The decline to the winter mini- 
