1 90 Jminial of Comparative Nciuvlogy and Psychology. 



it and ensheathe it, and form groups in the nuclear net. That which 

 clings to the chromosomes become modified to form the "Halbspindel 

 fasern." As the spireme splits, nucleolar substance still persists 

 around the daughter spiremes. This tends to collect at the middle of 

 the curved chromosomes which are turned with the convexity towards 

 the centrosphere. As the daughter spiremes separate, nucleolar sub- 

 stance unites with the linin to form the rays of the central spindle. 

 The linin in this phase stains slightly deeper than the cytoplasmic 

 reticulum but not so deeply as does the nucleolar substance. It is only 

 in the telophase stage that the nucleolar substance, which has been 

 associated with the linin, becomes indistinguishable from it. 



There seems to be conclusive evidence, therefore, that the nu- 

 cleolus of the adult nerve cell is a heterogeneous structure with an 

 oxyphile center which is structurally and chemically allied to the linin, 

 and with a peripheral zone of basophile chromatin. 



T/ic Ccntrosomc. 



Holmgren finds that the centrosome in the spinal ganglion cell of 

 Lophiiis is located in the center of the cell. It forms the center of the 

 concentric circles and radial "Ziige" of the cytoplasm. Holmgren 

 suggests that, since its reproductive function must have ceased, and 

 since it holds this constant relation to the trigroid substance, it is prob- 

 ably concerned in the nutritive functions of the metabolism of the cell. 

 The object which Lenhossek first interpreted as the centrosome in 

 the spinal ganglion cell of Raiia is, according to Holmgren, nothing 

 other than a section through an invaginated trabecula of the capsule. 



KoLSTER identifies the centrosome in the nerve cells of Pctromy- 

 zon even in unstained preparations, but it is not located in the center 

 of the cell. The centrosphere is surrounded by an irregularly shaped 

 mass of granules which are arranged in the form of a dense reticulum, 

 which we have already discussed in connection with the ground sub- 

 stance of the cytoplasm. The interior of the body in unstained prep- 

 arations appears as dark, circular lines separated by bright points. In 

 other methods, it appears as a circular space in which the centrosome 

 lies. 



The centrosome in the nerve cell of the dog and rabbit infected 

 with rabies has been studied by Nelis. He holds that the organ is 

 not visible in the normal nerve cells of mammals, but that it is brought 

 into plain view during chromatolysis which accompanies rabies. He 

 suggests that this reappearance of the centrosome immediately before 

 the nucleus atrophies indicates a tendency toward cell division at that 



