THE ABSORPTION OF FAT BY FRESHWATER 



MUSSELS. 1 



E. P. CHURCHILL, JR. 



INTRODUCTION. 



The present paper embodies the results of the first of a series 

 of investigations designed to ascertain whether or not animals 

 living in the water use food which is in solution in the surrounding 

 medium in addition to "formed" food such as plankton, etc. 

 If it is found that such food in solution is used, it is of importance 

 to learn whether it is absorbed by the alimentary tract alone or 

 to some extent by the epithelium of the outer body walls, espe- 

 cially that of the gills in the case of mussels. 



Putter ('08) was the first to advance the theory that food 

 could be so taken. He based his conclusions in part on a com- 

 parison of the amount of carbon necessary for the maintenance 

 of the organism with the amount furnished by the plankton. 

 Putter considered the latter too small for the needs of the animal 

 and argued that it must use some carbon which is in solution 

 in the water, resulting from the decay and disintegration of 

 organic life. He further stated that the amount of material 

 found in the alimentary canal is never large enough to supply 

 the requisite quantity of carbon. Besides the alimentary canal, 

 the uncutinized epithelium of the outer surface of the body, 

 -especially that of the gills, was thought to function in absorbing- 

 dissolved food. This process went on in addition of course to 

 .the digestion of "formed" food by the alimentary canal. Putter 

 'concluded that the above conceptions applied to Protozoa, 

 Porifera, Echinoderms, Crustaceans, Mollusks and Fishes. He 

 tested the matter experimentally in two ways: first by noting 

 that goldfish and perch lived much longer in solutions of aspara- 

 gin, somatose and glycerin than in tap water: secondly by com- 



1 Contribution from the United States Biological Station, Fairport, Iowa. 

 (Two of the experiments were carried out at the zoological laboratory of the Johns 

 Hopkins University.) Published by permission of the Commissioner of Fisheries. 



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