404 E. p. CHURCHILL, JR. 



in the water use, in addition to 'formed' food, nutriment which 

 is in solution in the surrounding medium. He wished also to 

 put to the test Putter's assumption that some of such nutri- 

 ment is absorbed directly by the cells of the outer body walls, 

 especially by those of the gills. 



Piitter ('06) was the first seriously to advance the theory 

 that food could be so taken. He based his conclusions in part 

 on a comparison of the amount of carbon necessary for the main- 

 tenance of the organism with the amount furnished by the 

 plankton. Putter considered the latter too small for the needs 

 of the animal and urged that it must use some carbon which 

 is in solution in the water, resulting from the decay and disin- 

 tegration 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 ali- 

 mentary 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 was considered to 

 go on in addition of course to the digestion of 'formed' food by 

 the alimentary canal. Putter concluded that the above con- 

 ceptions applied to Protozoa, Porifera, Echinoderms, Crusta- 

 ceans, Mollusks and Fishes. He tested the matter experiment- 

 ally in two ways: first by noting that goldfish and perch lived 

 longer in solutions of asparagin, somatose and glycerin than in 

 tap water: secondly by comparing the amount of oxygen needed 

 to oxidize the lost weight of tissues of actinians, tunicates and 

 fish while kept in their natural medium, with the amount of 

 oxygen actually used. As the latter was found to be greater 

 than the estimated quantity needed he concluded that the extra 

 oxygen was used in oxidizing some food that had been taken 

 from the water where it had been present in the form of a solute. 



Lohman ('09) estimated the amount of plankton found in 

 sea-water from various parts of the ocean and concluded that 

 plankton comprised the main source of the food of aquatic 

 forms. He quoted Henze's researches as showing that there 

 is present in sea-water no appreciable amount of carbon com- 

 pounds in solution. 



