66 'Journal of Comparative Neurology and Psychology. 



degree of accuracy in the work it was found desirable to bring the 

 animals into the laboratory and keep them under definite environ- 

 mental conditions, which could be more easily controlled. The 

 temperature and surroundings were generally more uniform than 

 they would have been outside of the building. The animals were 

 kept in moist boxes or glass dishes. Some were fed upon grass 

 or chestnuts; others were starved. At intervals animals were 

 taken from both the fed and starved groups and their nerve cells 

 studied, either in sections or in the live condition. 



Limax. — The remarkable appearance of the vacuoles and gran- 

 ulations in the nerve cells led us to make a series of tests with a 

 number of fixing agents in order to assure ourselves that we were 

 dealing with actual structures and not artefacts due to faulty fixa- 

 tion or preservation. 



The following agents were employed : Carnoy's fluid, Petrunke- 

 vitch's solution, picro-nitric acid, Flemming's strong solution, 

 osmic acid and absolute alcohol. The vacuoles and the bodies 

 contained within them appeared with a constancy that was remark- 

 able. 



Effects of starvation and feeding. — Specimens of Limax taken 

 in the early spring as soon as they emerge from their hibernation 

 exhibit in the cytoplasm of the nerve cells collections of vacuoles 

 of various sizes, scattered about in various parts of the cell. Some- 

 times the whole cytoplasm appears to be peppered with them; 

 sometimes they are packed together with their thin walls touching 

 each other in such a way as closely to resemble in appearance a 

 mass of soap bubbles. In some of the vacuoles small granules of 

 various shape may be found. The granules are, however, not 

 to be found in all of the vacuoles at this time. Fig. i of Plate I 

 is a photograph showing the strongly vacuolated condition which 

 may be seen in the cells and also indicates the presence of some 

 of the granules mentioned in certain of the vacuoles. 



The other cell structures do not show any especially important 

 features. The nucleus is large and well defined. In some cases 

 the cytoplasm appears to be somewhat shrunken, but this is far 

 from being a constant character. 



Later in the spring animals taken into the laboratory and stud- 

 ied, or animals which have been kept in the laboratory and fed upon 

 grass show that the number of solid bodies within the vacuoles has 

 increased. This increased number is found to hold throughout 

 the summer and fall of the year. 



