56 'Journal of Comparative Neurology and Psychology. 



(vesicular), especially so toward the distal pole. A thin peripheral layer of finely 

 granular cytoplasm is always present. The vacuoles do not seem to have any 

 definite grouping, but such groupings as exist are explained as corresponding to 

 the different physiological states. 



Certain bodies occur in these ganglion cells in Lineus which are absent in all 

 of the cells in Cerebratulus. These bodies are frequently larger than the nucleolus 

 and of a spherical or oval shape, and are not refractive. After the use of a double 

 stain they stain usually with eosin, sometimes with haematoxylin, but always more 

 intensely than the surrounding cytoplasm, though seldom as deeply as the nucleolus. 

 Structurally, they are homogeneous, with a peripheral membrane, which may be 

 scarcely discernible or in other cases, of considerable thickness; this membrane 

 always stains more intensely than the enclosed portion, and forms a boundary 

 against the surrounding cytoplasm (Fig. 5). These bodies do not occur in all 

 cells, but only in about one-sixth of the total number; when they are present, it 

 may be but a single one, more frequently four or five, apparently never more than 



II 





e 9. 



Fig. 5. Fig. 6. 



Fig. 5. Lineus gesserensis. Ganglion cell of the third class, showing the presence of vacuoles, some 

 of which contain differentiated granules. After Montgomery ('97, Fig. 9). 



Fig. 6. Nereis, brain cell of sixth class. Nucleus lies in narrow end surrounded by granular cyto- 

 plasm, while in the other end there is a large vacuolar space. After Hamaker ('93, Fig. 17). 



fifteen. There is also no regularity in their distribution, such as a concentric or 

 radial arrangement, and in the same cell they are usually of various sizes and of 

 different staining power. To these cytoplasmic bodies may be appHed the term 

 chromophilic corpuscles, to distinguish them from the chromophilic granules in 

 the ganglion cells of other animals. 



Rand ('01) reports vacuoles and gives an analysis of the cytoplasm as follows: 

 Very little can be said as to the finer structure of the cell protoplasm in the Lum- 

 bricidae. The most careful examination fails to reveal its precise nature. It 

 varies in degrees of homogeneity somewhat according to the size of the cell. In 

 the smaller cells, it usually appears compact and fairly homogeneous. In larger 

 cells, it is much less homogeneous, and there is a tendency toward the formation 

 of large vacuolar spaces. The substance of the fixed cytoplasm, as it appears to 

 the eye, may be said to be of four kinds. There is (i) a perfectly homogenous 

 "ground," represented by the lightest areas in the figures; (2) material which gives 

 the impression of being very finely granular; in the smaller cells this is quite evenly 



