Bull. U. S. B. F., 1921-22. (Doc. 922.) 





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Fig. 194.— Photomicrograph of a bit of tow material collected over a mussel bed near Woods Hole, Mass. 

 Fig. 195. — Photomicrograph of a bit of material from the stomach contents of a mussel. Plankton organisms 



and detritus are present in about equal amounts. 

 Fig. 196. — Photograph of the fresh fecal discharges of a mussel which was cast out in ribbonlike form. Slightly 



enlarged. 



Fig. 197. — Photomicrograph of the feces of a mussel after the ribbonlike discharges have disintegrated. Note 



the finely divided state of the material compared with that of the stomach contents. 



