ABSORPTION OF NUTRIMENT BY MUSSELS 423 



In the case of mussels in particular it is very probable that 

 considerable nutriment is in solution in the water in which they 

 live. While no analysis of the water has been made thus far 

 in the investigations, the Mississippi River, as everyone knows, 

 drains a vast area of land from which refuse from decaying ani- 

 mal and vegetable material is collected in very great abundance. 

 The dead bodies of aquatic forms of many sorts add to this sup- 

 ply. The mussels are bottom-Uving organisms and come into 

 contact with decaying and dissolving organic matter which 

 is lying on or being slowly moved along the substratum. Solu- 

 tions or colloidal suspensions of the proteins must certainly 

 be present in some abundance. As the water is slightly alkaline 

 some of the fat from decaying organisms is probably saponified 

 and thus distributed throughout the water instead of rising 

 to the surface where it would be inaccessible to many forms. 

 . In general the question of whether or not a particular aquatic 

 animal absorbs nutriment from solution by means of the ali- 

 mentary canal and the outer body walls probably depends on 

 the presence or absence of dissolved substances in the water in 

 which the animal in question lives. Fresh-water mussels can 

 absorb nutriment which is in solution in the water and it seems 

 very probable that other forms likewise possess this ability. 



THE JOURNAL OF EXPERIMENTAL ZOOLOOy, VOL. 21, NO. 3 



