246 THE UNIVERSITY SCIENCE BULLETIN. 



tract was packed with pale green matter like the culture! This proved 

 to consist almost exclusively of the clear filaments of Mougeotia, the 

 contents of the cells of which were in a state of disintegration. The 

 free granular green matter was obviously derived from contents of the 

 Mougeotia cells. No animal organisms or their remains found in these 

 examinations. 



Culture 16126. (Rivularia.) 



History and Diagnosis. A porcelain-lined, gi-anite-ware pan, which 

 had been used for some time as a watering vessel for the birds and 

 chickens, contained a layer of brownish material over the bottom and up 

 the sides. Upon examination the material was found to consist of 

 debris and Rivularia natans, no animals present. 



Cofixids Added. Eggs of an undetermined Corixid were added and 

 reared to second instar, when all died. The experiment was repeated 

 with similar results. The water was not changed as frequently as might 

 have been desired. Adults of R. acuminata and A. altemata failed to 

 live more than a few days in this culture. 



Culture 1754. (Slime Diatoms.) 



History and Diagnosis. The rocks of upper Fall Creek were covered 

 with long, brown strings of gelatin in March. This was found to con- 

 sist of great quantities of the diatoms, Meridion, Fragilaria, etc., some 

 filamentous Algae present but scattered. Placed some small stones, coated 

 vdth this material, in a battery jar. 



Corixids Added. Placed Corixids here and they promptly began feed- 

 ing. When examined surprisingly few diatoms were present, but quan- 

 tities of filamentous algae, Mougeotia and Zygnema. 



For example, one female A. alterno.ta had the fore part of the stomach 

 packed with filaments of Zygnema as long as the entire mid intestine. 

 This series shows selection in favor of the filamentous algae with dis- 

 crimination against the gelatin embedded diatoms. 



Culture 17144. (Ankistrodesmus.) 



History and Diagnosis. Removed the gold fish from a jar in which 

 they had lived for a long time. The jar and rocks were covered with 

 dark-green growths. The water was very green. This was replaced 

 by fresh water. The green growth was dominantly Ankistrodesmus 

 falcatus. Some Scenedesmus and diatoms present as well as Cosmarium 

 and Tetraspora. 



Corixids Added. Twenty nymphs of P. buenoi added. Examined 

 their stomach contents from time to tim.e and they were always full of 

 green chlorophyll material with Ankistrodesmus dominant and other 

 Algae present with an occasional rotifer. Green plants are taken first 

 hand and in quantities. 



Culture 16169. (Botryococcus pure.) 



History and Diagnosis. Botryococcus (a little alga in gelatin.) This 

 culture was pure and growing in Knap's solution. 



Corixids Added. The bugs always died within a day or so. 



