221 



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 

 ( '98) 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: 

 Flosculana ornata Ehrbg., Limnias ceratophylli Schrank, Cephalosi- 

 phon limnias Ehrbg., CEcistes intermedius Davis, 0. mucicola Kell., 

 Pedetes saltator Gosse, Furcularia forficula Ehrbg., F. longiseta 

 Ehrbg., Eosphora aurita Ehrbg., Diglena grandis Ehrbg., D. catellina 

 Ehrbg., D. biraphis Gosse, Ccelopus tenuior Gosse, Scaridium longi- 

 caudum Ehrbg., Distyla gissensis Eckstein, D. okioensis Herrick, 

 D. stokesi Pell, and D. hornemanni Ehrbg. 



GASTROTRICHA. 



Ch&tonotus sp. occurred singly in the plankton August 29, 1896, 

 July 30, 1897, and February 15, 1898, with a temperature range of 

 32.5 to 84. 



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 Entomostraca appear in every collec- 

 tion at all seasons of the year. The decline to the winter mini- 



