228 Papers from the Department of Marine Biology. 



red or scarlet, while all plasmosomes will appear of a very light and 

 delicate pink. This is in spite of the larger size of the plasmosome, 

 which if it had an equal chemical affinity for the dye would stain much 

 darker on account of its much greater diameter or thickness. The same 

 is true of sections stained with safranin. 



In the fresh specimen the structures that support these chromatin 

 nuclei are almost invisible. With strong oblique lighting a slight 

 suggestion of a supporting framework 'or reticulum of linin can be seen. 

 In the fixed specimens, however, such a supporting reticulum appears 

 and with most fixations it can be seen that the chromatin nucleoli are 

 embedded in the larger masses of linin that lie at the centers of this 

 reticulum. Further, it may be seen that the linin substance is arranged 

 in a radiating fashion about the chromatin nucleolus in a way to form a 

 sphere which is about the size of, or a little smaller than, the plasmosome 

 and which has a fairly clear boundary or limit. This sphere, when it 

 contains the " perichromatin " of Magini, together with the central 

 granules which have been described as the karyosomes or chromatin 

 nucleoli, represents the " spherule" of Magini, which he has so accu- 

 rately described in his paper as the new substance of the electric motor 

 nerve-cell. I have myself also observed and described in a histological 

 text-book (Dahlgren and Kepner) (11) similar or probably identical 

 structures in the large nerve-cells found in the motor ganglia of Cepha- 

 lopoda. 



I have been unable to prove any chemical or physical difference 

 between the achromatic substance of these spheres and the remainder 

 of the linin reticulum. The only differences observable are mechanical 

 the larger size of the sphere and its fairly regular radial arrangement. 

 Its principal and only chemical (?) mark of distinction from the re- 

 maining linin is the fact that in some fixations it holds the substance 

 called by Magini the "perichromatin," which he shows to have impor- 

 tant staining qualities that differ from the other colorable materials in 

 the cell. Its strong inclination to dissolve in certain media make it 

 somewhat hard to show. Magini showed it best, according to his 

 decriptions (unfortunately he had no figures) , by fixation in osmic acid 

 and staining in safranin. In my preparations it is best seen in iron 

 hematoxylin stains after sublimate and formalin-alcohol fixations. 

 Some of the best fixations, as Flemming and Bouin, show it entirely dis- 

 solved, or at least not visible in any manner whatever; other stains 

 show it weakty visible, while some show it as a dense cloud gathered in 

 a sphere about the karyosomes and staining a decidedly different tint 

 from them. 



Scattered in a spherical cloud in the mass of perichromatin are a 

 number of small granules, much smaller than the central karyosome 

 and also not strictly spherical in shape, as it is. These granules I shall 

 denote as the perichromosomes. They may be angular in shape and 



