334 Illinois State Laboratory of Natural History. 



fine, in longitudinal rows, often with intervening bristles ; 

 body more or less contracted when free-swimming; when 

 attached, often protected by a tubular gelatinous sheath. 

 6-i. S. polymorphus 0. F. Mijll. 



Not very common at any time, occurring now and then 

 from April to July in towing and vegetation collections taken 

 in lakes. In an aquarium in the zoological laboratory of the 

 University this species was very abundant, large colonies 

 more than half an inch in diameter being formed, consisting 

 of a gelatinous substance in which the animals were fixed. 



65. S. roeselii Ehkbg. 



Not common ; found in towings and among vegetation in 

 the river and in Quiver Lake. 



66. S. barretti Barrett. 



A few examples seen in March from the river at E. This 

 is closely allied to S. rocseUl, but to me the two appear dis- 

 tinct. 



67. S. cceruleus Ehrbg. 



Found in some catches from along the shores of Quiver 

 Lake in May, in one of which it was common. This form 

 also occurred in aquaria at the University laboratory. Small 

 glass jars were filled with water containing some of them, 

 and after these had stood for several weeks the inner surface 

 of the jars was fairly lined with the Stcntor. Tliey reproduce 

 very rapidly, and with a little care a constant supply for 

 laboratory use can be kept on hand. 



68. S. igneus '? Ehrbg. 



A Stcntor was found several times in the towings, which I 

 have doubtfully referred to this species. It was found once 

 in Dogfish Lake in August, and afterwards in towings from 

 the river at E from November to January, being abundant in 

 December. 



69. Stentor sp. 



A small green species was found in a weedy bay — the 

 "Pumpkin Patch"— at the head of Quiver Lake; but was 

 not definitely determined. _ 



