228 WILLIAM RAY ALLEN. 



A quantity of Spirogyra and other filamentous algae was cut 

 as finely as possible with scissors, then macerated with a pestle. 

 Examined microscopically there were found fragments of cell- 

 wall varying in size, fragmented chloroplasts, and pyrenoids. 

 Without screening, this material was fed, in considerable quantity 

 to starved mussels. The water was agitated occasionally so as 

 to keep some of the macerated material in suspension. One mass 

 of alga had been taken from a dish in which decomposition had 

 gone far. Although the mussels held the siphons nearly closed 

 in the decomposing culture, they nevertheless ingested sufficient 

 alga to answer the purpose of the experiment. Feeding the de- 

 composed alga is comparable to the feeding of infusions, and the 

 animals reacted similarly. In all cases of feeding infusion, de- 

 caying alga, and the feeding of mussels below the sewer outlet in 

 Pocahontas creek, the regenerated crystalline styles had the same 

 milk-white appearance. Thus there is no doubt that in all cases 

 the color was due to bacteria. Mussels fed upon macerated 

 fresh Zygnenia had clear, and colorless or green, styles. 



In one mussel fed upon a maceration of Spirogyra the partially 

 regenerated style had a large core, and only two or three thin 

 layers of style substance. This gave it the proportions and ap- 

 pearance of a rubber tube. When stretched out in a watch crystal 

 and placed under the weight of a cover'glass, the contents slowly 

 oozed out at a broken point. The core was then seen to consist 

 almost entirely of pyrenoids (or like bodies) closely packed, and 

 in very great quantity. Their mass had a gray-yellow color. 

 Only here and there was there a minute spot of green. Not a 

 trace of cell walls or of a spiral fragment of chloroplast was 

 found here or in the stomach. We have then another case of the 

 rigid selection of food particles, and a little suggestion of the 

 character of the materials which are capable of inciting the secre- 

 tion of a new style. Again we have evidence that the gill is 

 capable of taking very small particles from the water. 



In a decaying macerated Spirogyra culture several starved 

 mussels kept the siphons almost entirely closed. When a few c.c. 

 of alcohol were added they shortly began and continued siphoning 

 vigorously. Yet the food sorting mechanism functioned normal- 



