ABSORPTION OF NUTRIMENT BY MUSSELS 411 



which had been in the solution revealed many fat droplets in 

 the cells on the side next to the body. No fat droplets were 

 found in the cells of the corresponding part of the other mantle 

 which had not been in the solution. Some of the cells of the 

 mantle which had been in the solution are represented in figure 

 9, while figure 10 shows cells of the other mantle which had re- 

 mained in the air. In all these cases in which the mussels were 

 suspended in such a manner as to allow only a portion of their 

 body to come into contact with the solution, the oral and anal 

 openings were above the solution so that none of the solution 

 could have entered the alimentary canal directly. In the case 

 last mentioned, in which one mantle of the mussel was immersed 

 in the solution and compared with the other mantle of the same 

 mussel, this mantle not having been immersed, direct proof 

 of the absorption of fat from the solution by the epithelial cells 

 of the mantle is given. In all cases in which one mussel is used 

 as a control for another the objection can be raised that by chance 

 a naturally fatter individual was chosen to be kept in the solu- 

 tion. But that objection can not hold in this case as it is hardly 

 supposable that corresponding parts of the two mantles of the 

 same mussel would differ in fat content as markedly as indicated 

 in figures 9 and 10. 



Protein 



The problem of the absorption of protein was first attacked 

 by means of the 'starvation' method. Five mussels were kept 

 in solutions of egg albumin and five in filtered water. Both 

 experiments were started on the same day and at intervals 

 one individual was removed from the solution and one from 

 the water at the same time and their tissues fixed and sectioned. 

 Bouin's fixing fluid was used for this work and the sections were 

 lightly stained with haematoxylin and eosin. One pair of mus- 

 sels was killed at the expiration of ten days, other pairs at the 

 end of thirty, forty-five and fifty-eight days. One of the in- 

 dividuals in filtered water died on the twentieth day. The tissues 

 of the mussels were compared by the study of the sections for 

 the purpose of discovering any possible difference in the degree 



