420 . E. p. CHURCHILL, JR. 



ently transported while floating in the plasma of the blood. 

 A description has been given above of the discovery of fat drop- 

 lets, granules of albumin or of starch, as the case might be, 

 in the corpuscles of the mussels which had been in the solu- 

 tions. It was also found that the corpuscles, in' addition to 

 pressing closely against the bases of the cells of the gills, actually 

 wandered out between the cells in such a manner that their en- 

 tire surfaces were in touch with the cells, the corpuscle lying 

 in a sort of cup between the contiguous cells. This phenomenon 

 is illustrated in figures 15, 16 and 17. In great numbers of 

 eases the corpuscles were found pushed out between the cells 

 in such a way as to be enthely surrounded. In other instances 

 a corpuscle might be observed partially surrounded as in figure 

 15, the process of fixation having killed it at the moment of 

 entrance to or exit from between the two cells. Undoubtedly 

 a position in w^hich the corpuscle is entirely surrounded by the 

 epithelial cells affords more surface for the exchange between 

 the cells and the corpuscle not only of materials concerned in 

 respiration, but also for the reception by the corpuscle of food 

 material absorbed by the cells of the gill. Similar behavior 

 of the corpuscles was not noted in parts of the body other than 

 the gills. 



SUMMARY AND DISCUSSION 



The above results leave no doubt of the fact that mussels 

 may make use of some kinds of food which are in solution in 

 the water. A part, probably a small one, of such nutriment 

 can be taken up directly by the outer epithehal cells of the body. 

 As these animals are provided with a well developed digestive 

 apparatus we may suppose that the absorbing power of these 

 outer epithelial cells is a property that has been retained from 

 a more primitive state in which the cell was less highly specialized 

 and that this property is not a special adaptation correlated 

 with the lack of a functional digestive system. 



The nutriment taken up from the solutions by the mussels 

 by means of the alimentary canal was no doubt absorbed by 

 the cells lining the intestine m the usual manner in which 'formed' 



