232 



their quarters to any considerable extent. No food of any sort was 

 introduced at any time. At intervals -specimens were removed, the 

 nerve ganglia dissected out, and the nerve cells examined for possible 

 changes. In accordance with the observation previously reported, it 

 was found that there was a regular decrease in the amount of pig- 

 mented granules found in the cells as the length of the period of 

 starvation increased. The last specimen was killed on the 15th of 

 August 1909. This specimen was examined with great care, for it 

 was evident that the animal would not have lived for a much longer 

 time, a number of deaths from starvation having occurred in the colony 

 within a few days of the killing of this animal. The nerve cells 

 showed an almost entire lack of pigment matter. At the same time 

 the number of transparent vacuoles in the cytoplasm of the cells was 

 very large. These vacuoles were located in a zone of the cytoplasm 

 extending from near the cell membrane about one half the distance 

 to the nucleus. Their location was, then, the same as that in which 

 the solid granules had been found previously. So far as we have 

 been able to determine, there was no shrinkage of the cell as a whole, 

 nor of the nucleus. 



Summary and Conclusions. 



1. The presence of granules, either pigmented or unpigmented, 

 in the ganglion cells of invertebrates is general so far as our observ- 

 ation has gone. They have been demonstrated in several groups 

 of molluscs, worms, etc. 



2. An equally constant structure of the cytoplasm is the vacuole. 

 In some cases vacuolation may be a mark of pathological conditions ; but 

 it is more generally a sign of previous activity on the part of the 

 cell. The contents of the vacuoles represent granular matter in pro- 

 cess of transformation to be used as food matter by the cell proto- 

 plasm. 



3. The granules may be caused to break down and contribute 

 their materal under any condition which uses up the ordinary sup- 

 plies of energy, as for example under excessive work or long continued 

 starvation. 



