Smallwood and Rogers, Molluscan Nerve Cells. 69 



was allowed to continue until the body had been completely re- 

 placed by the more transparent liquid mass. At this time the 

 current was stopped. A continued study of the cell showed that 

 in the same vacuoles where the disappearance of the bodies had 

 been noted there was later a reconstruction of the solid body. 

 Within an hour or two the solid masses had again become estab- 

 Hshed in the cells. These bodies were, however, not the same 

 bodies as had existed in the cells previous to the stimulation, as 

 they exhibited entirely different forms. 



That we have here substances in the cell which are intimately 

 connected with the normal activities of the cell seems to be demon- 

 strated. As to the chemical nature of these bodies we have only 

 little knowledge. The fact that they are more or less darkened by 

 osmic acid would indicate that they are of a fatty nature. Fur- 

 ther we can not say at the present time. 



VI. PIGMENT. 



Nansen ('87) was, so far as we are aware, the first to give an accurate account 

 of the yellow pigment granules existing in certain of the invertebrate nerve cells, 

 although such granules had been observed before. He found in the nerve cells of 

 Patella plenty of large yellow granules lying in the cytoplasm. These granules 

 had a variable size, and no regular shape, being sometimes spherical, sometimes 

 square or polyhedral. They looked as if they had been produced by the coagula- 

 tion of a homogeneous yellow substance. The granules were sometimes found 

 scattered through the whole mass of protoplasm, but more frequently were con- 

 centrated in special parts of the cells, especially in the neighborhood of the nucleus. 

 Plenty of similar smaller and larger granules were also to be found outside the 

 ganghon cell. They frequently occurred in such numbers that one, for a time, 

 could feel disposed to believe that they belonged to a substance extending through 

 the whole nervous system. Nansen was convinced that they were either exuded 

 from cells, or that they sprang from destroyed cells. He had observed such a sub- 

 stance exuded fromthe protoplasm of the cell. Fig. 9 represents such a case. The 

 substance here occurred inside as well as outside the cell. The granules were 

 concentrated toward the part of the cell surface where they were probably to be 

 exuded. Outside the cell they were united into larger pieces of irregular shape. 

 The granules were situated not only near the surface of the cell but also occurred in 

 the mesial parts of the protoplasm. Nansen recognizes that the granules gave 

 the yellow color to the nervous system of Patella, as well as other molluscs. 

 He thought the yellow color to be due to a substance allied to or similar to haemo- 

 globin, and also believed that the granules contained fat. He found difficulty in 

 recognizing these granules in the sections of nerve cells. As to function, he believed 

 them engaged in the nutrition of the cell. 



McClure ('97) in connection with his studies of the chromophile granules 

 mentions the existence of pigment granules in the cells of gasteropods, but gives 

 them no further attention. 



