ABSORPTION OF NUTRIMENT BY MUSSELS 407 



to Dr. H. S. Jennings and Dr. R. E. Coker for their suggestions 

 and interest in the work: to Dr. G. L. Houser for hbrary facih- 

 ties at the University of Iowa; and to Mr. A. F. Shira, Director 

 of the Biological Station at Fairport, Iowa. 



MATERIALS AND METHODS 



The mussels upon which the investigations were carried out 

 were individuals selected from the more common species found 

 in the Mississippi River near Fairport, Iowa. Adult specimens 

 were employed in the following experiments. Care was exer- 

 cised to choose non-gravid mussels which were in a seemingly 

 healthy condition, 'shoulder-raked' or hand collected individ- 

 uals being used in preference to those dragged out of the water 

 by 'crow-foot' hooks. 



At Fairport soft water was used for the work with fat, for 

 the reason that the soap was more soluble in it than in river 

 water. For the experiments with protein and starch filtered 

 river water was used. At the Johns Hopkins Laboratory, 

 where the work concerned only protein and starch, either city 

 tap water or Chattolanee spring water was used. 



The mussels experimented with were kept in glass aquaria 

 of about 5000 cc. capacity. Control individuals in filtered 

 water were kept side by side with those in the solutions. The 

 solutions were changed daily in most cases. In some of the 

 experiments with protein the changes were made twice daily. 

 By this procedure the protein was prevented from undergoing 

 marked decomposition. As the mussels are accustomed to 

 a current of water this method of manipulating the aquaria 

 seemed to be the closest approximation to natural conditions 

 which it was possible to obtain in the laboratory. 



For the experiments with fat a 'non-alkaline' soap commer- 

 cially prepared from olive oil was used. This was done to avoid 

 the free alkali and oil present in the saponified olive oil employed 

 in the earlier investigations. The strength of the solution used 

 was 0.002 of one per cent. The tissues of various portions of 

 the mussels experimented with were sectioned by the freezing 



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



