THE ABSORPTION OF FAT BY FRESH-WATER MUSSELS. 69 



paring 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 was 

 present in the form of a solute. 



Knorrich (10), working with Daphnia, which lived 14 days in 

 sterilized hay solution, concluded that nutriment was absorbed 

 from the solution. 



Kerb (10) kept eels in sugar solution and noted no diminution 

 of the amount of sugar from day to day. He obtained similar 

 results while working with Corethra larvae in sugar solutions. 

 Also he found that Daphnia lost in dry body weight as rapidly 

 in solutions of peptones as in tap water. 



Wolff (10), working with Simocephalus, found that it lived 

 twice as long in bacteria-free water, which contained some dis- 

 solved carbon compounds, as it did in tap water. He made no 

 observations as to body weight lost or gained. 



Lipschiitz (13) reviewed the entire subject including his own 

 previously published experiments along that line and offered 

 criticism of Putter's work. Lipschiitz noted that fish and eels 

 when kept in nutrient solutions lost as much weight as in tap 

 water. He also thought that Putter overestimated the amount 

 of material in solution in the water and underestimated the 

 carbon content of the plankton. His general conclusions are 

 the opposite of those of Putter. 



Lund 1 found that if Protozoa are kept in a weak soap solution 

 they will absorb fat from such solution through their body walls. 

 At his suggestion the fats used in the following experiments were 

 rendered soluble in water by saponification. 



I am especially indebted to Dr. Caswell Grave, at whose sug- 

 gestion the work was undertaken, for his advice and aid on 

 many occasions and his supervision of the preparation of the 

 manuscript. I also desire to express my obligations to Dr. E. J. 

 Lund for suggestions concerning some of the chemical reactions 



1 Dr. Lund's paper is not yet published, his results having been communicated 

 to me verbally. 



