22O WILLIAM RAY ALLEN. 



latoria (small amount), Sccncdesnnis, Synedra, and Tabellaria. 

 Considerable debris, both organic and inorganic, was found, and 

 some fragments of considerable length. 



In the case of those fed upon " bolted " water considerable 

 amounts of green were found in the intestine, and the styles were 

 flaccid and green. No large particles were obtained. Tabellaria, 

 Diatoma, and Navicula occurred, but it was only very small spe- 

 cies in each case, and no coherent members of colonies. Very 

 little inorganic stuff was found, but many organic fragments, 

 some of them partially digested. The smaller flagellates were 

 proportionately more numerous than in the checks. Naturally 

 the diatoms were of the solider, creek type, and none of the grace- 

 ful lake forms adapted for flotation. 



(&) The Feeding of Seivage. 



The presence of Oscillatoria may be taken as an index of the 

 amount of sewage in the food. It also shows a well-defined 

 gradation in the several feeding stations: (i) no Oscillatoria 

 was recorded from the experimental animals above the sewer 

 outlet; (2) very little appeared in the checks kept in the un- 

 screened stream at this point; (3) somewhat more Oscillatoria, 

 consisting of very incomplete filaments, was seen in the experi- 

 mental animals below the sewer ; and (4) the checks below the 

 sewer contained numerous large fragments of Oscillatoria, and 

 many relatively large bits of debris never met with elsewhere. 



Mussels which had been kept in the mouth of the creek for 

 several weeeks prior to these experiments were opened at the 

 same time. The styles were well formed and without color. On 

 various occasions the styles of the experimental animals reacted 

 differently. At one time all of the styles were whitish when par- 

 tially renewed, having a distinct white, spiral core. In those most 

 perfectly formed the white color was disappearing, and the entire 

 mass was becoming more solid and more hyaline. On other occa- 

 sions the newly formed styles were of the typical amber hue 

 which suggested diatomin. Subsequently mussels opened here 

 contained sometimes whitish, sometimes colorless styles. At 

 times freshly formed styles were found which were green in the 



