324 Illinois State Laboratory of Natural History. 



times of day, except in case of a storm, these and related 

 species appear in vast numbers at the surface of the water, 

 forming the "water-bloom." In the vicinity of the Station, 

 this frequently formed green, brown, or red patches along the 

 shores, or drifted down the main channels in long streaks or 

 broad areas, not dense enough to be evident when close at 

 band but very noticeable if viewed obliquely from a short 

 distance. On small pools the water-bloom often becomes a 

 dense green, paint-like, scum. It frequently consists in great 

 part of some single species. EiKjlcna is readily eaten by 

 rotifers and by some Protozoa. The rotifer Eosphora aurita 

 was found in the water- bloom. 



29. E. viridis Ehrbo. 



During the warmer season, from May to September, this 

 was frequent to abundant in the towings from most of the 

 substations, and very abundant in the water-bloom that was 

 examined. This species is highly changeable in shape. 



30. E. spirogyra Ehrbg. 



A few were found in a towing from Phelps Lake in July. 

 This pretty species preserves its form better than the pre- 

 ceding, is slightly thicker in proportion to its length, and its 

 surface is marked with oblique rows of small bead-like eleva- 

 tions. 



31. E. acus Ehrbg. 



Occurred from July to September, in small numbers, in 

 towings from the river and several lakes. It is very slender, 

 ending posteriorly in a sharp point, and is persistent in 

 shape. 



32. E. oxyuris Schmarda. 



Frequent and often common during about the same period 

 as that recorded for riridis; occurring from June to October. 

 It is elongate, obliquely striate, often spirally contorted. , A 

 fine species, persistent in shape, and easily recognized. 



33. E. torta Stokes ('85). 



This small species was observed but once, namely, in a tow- 

 ing taken from Phelps Lake in July. It agreed in all par- 

 ticulars with Dr. Stokes's description, and the species appears 



