CoGHiLL, Stnict?irc of the Nerve Cell. 189 



exclude the possibility of such ruptures in the nuclear membrane as 

 Holmgren and Kolster describe. 



The Nucleolus. 



The behavior of the nucleolus in the spinal ganglion cells of Lo- 

 phius as described by Holmgren ('99) has already been mentioned in 

 the section relating to the nucleus. Regarding the finer structure and 

 chemical nature of the nucleolus the works of Kolster, Hatai and 

 Scott are noteworthy. 



In the spinal ganglion cell and the Freud' schen cells of Petro- 

 viyzon, according to Kolster, the nucleolus appears homogeneous only 

 in preparations fixed in sublimate and stained in iron haematoxylin. 

 In all other methods which the author used he found two rather sharp- 

 ly differentiated zones, a dark, relatively large central portion sur- 

 rounded by a shell of substance which stains more faintly than the 

 central body. In some preparations there appeared a granular, inter- 

 mediate zone between the central core and outer shell. Kolster is 

 inclined to interpret the nucleolus, not as a solid mass, but as a vacuole 

 with peculiar liquid contents. The reaction of the contents to reagents 

 accounts for the structural features which appear by different methods. 

 PuGNAT, on the other hand, considers that the central, granular ap- 

 pearance of the nucleolus is due to the presence of formed bodies. 



Scott ('99) and Hatai ('03) both demonstrate an oxyphile center 

 with basophile peripheral zone in the nucleolus. Only the basophile 

 part represents the chromatin, while the oxyphile center is the true 

 nucleolar substance. 



The behaviour of the nucleolus of the nerve cell during mitosis 

 has been carefully worked out by Hatai. While in the adult nerve 

 cell the larger part of the nucleolus stains blue with toluidin-erythro- 

 sin, in the germinal cells the entire nucleolus stains a deep red. In 

 the later telophase stage of mitosis the nuclear substance, which has 

 become closely massed around the chromosomes, dissolves and ac- 

 cumulates again in small spherical masses which collect near the cen- 

 ter of the nucleus. Each granule of this group sends out a process 

 from either pole. These processes from the various granules anasto- 

 mose to form a net with granules at the angles of the meshes. The 

 linin and the basophile nuclear substance now collect around this 

 group of acidophile granules to form the nucleolus of the adult nerve 

 cell. But if the cell is to divide again, the linin which has accumu- 

 lated around the nucleolus breaks up in the early prophase and the 

 nucleolar granules separate. As the spireme forms they collect upon 



