70 yourtjsl of Comparative Neurology and Psychology. 



Legendre ('o6) found in the nerve cells of Helix aspersa, Helix pomatia and 

 Arion rufus pigment granules of various sizes, sometimes isolated, sometimes 

 grouped together in irregular masses. The granules w^ere most frequently located 

 in the cone of origin of the axone, though they were sometimes arranged in con- 

 centric rows in the peripheral layer of the cytoplasm. Frequently they extended 

 out along the axis cylinder. Osmic acid alone or in combination attacked the 

 granules and stained them black at times; at other times they were unaffected. 

 Haematoxylin gave them a brown color. These reactions resembled those of the 

 lipochrome pigments observed in the nerve cells of a large number of vertebrates 

 and some invertebrates. The number of granules varied in different individuals, 

 and the author had failed to establish any connection between their appearance and 

 the physiological state of the animals. He says, "The role of the granules is not 

 known. One may consider them as a food, a reserve material, a functional pre- 

 cipitate, a product of disassimilation, a degenerative product. The multitude of 

 hypotheses tells us nothing concerning their composition, their variation or their 

 functions." 



Plaiiorbis. — In the preliminary study of the nerve cells of Plan- 

 orbis the same general methods were employed as in the case of 

 Limax. A number of fixing fluids were used and their compara- 

 tive effects carefully studied. The various cell structures appeared 

 almost equally well in the cells fixed by all the different agents. 

 From a study of a large number of sections it appeared that abso- 

 lute alcohol was at least as good as any other. For clearness and 

 sharpness of detail it could hardly he surpassed. One feature 

 should be mentioned. A long continued stay in alcohol is not 

 good for this material, as it tends to swell the pigmented bodies 

 in the nerve cells and to remove from them a portion of their color, 

 changing it from a bright golden brown to a lemon yellow. These 

 bodies are, however, clearly distinguishable in our sections, even 

 when the stay in the alcohol was somewhat prolonged. 



The vacuoles which formed so constant a structure in the nerve 

 cells of Limax are rarely found in the cells of Planorbis. When 

 present they are usually located in the end of the cell farthest from 

 the axone and very seldom contain pigmented granules, though 

 specimens have been found in which even in the living cell it was 

 possible to see these bodies within the limits of the vacuole. The 

 contents of the vacuole is a liquid of low viscosity, for the little 

 brown granules could be seen dancing with the characteristic 

 Brownian movements. In other parts of the cell where the bodies 

 do not appear in the vacuoles they lie perfectly at rest. 



Effects of starvation and feeding. — In Planorbis the number 

 and size of the pigmented granules depends upon the general 



