3i2 H. M. BERNARD. 



nerve-fibril ou tlie one hand, and into the cytoplasm on the 

 other, leaving the filament naked. This seems to me to be a 

 possible interpretation of the microscopic appearances. I 

 may add that we have already seen how the action of at 

 least one fixative, e. g. boiling corrosive sublimate, leads to 

 the displacement of chromatin along the connecting fibrils. 

 This appai-ently occurs on a large scale in retinas so fixed ; 

 some have the nuclei balled together into compact globules 

 of chromatin, others spread out into amoeboid masses united 

 by their processes into a network (see fig. 16). I propose to 

 follow up this subject as to the possibility of a stream of 

 chromatin passing along the nerve-fibrilla3, in another paper 

 dealing specially with the nervous system, and must content 

 myself here with making the suggestion as perhaps throwing 

 light upon the origin of at least part of the chromatin which 

 streams through the retina. 



In addition to the different forms above described under 

 which the chromatin seems to escape from the nuclei, viz. 

 as beads, as continuous streams clotting the connecting 

 filaments, and as crowds of microsomes forming the " Nissl's 

 Schollen," there is another method occasionally seen which 

 requires a good deal of further investigation. 



Variously sized, spherical, highly refractive masses, each in 

 a small clear vacuole, are met with outside the nuclei. I 

 have found them in the granular cytoplasm of the ganglionic 

 nuclei (fig. 20 a) and in the rods (Part II, figs. 29 c, d,f). 

 In both of these situations they have been seen by others. 

 When seen in the former situation they have usually been 

 called ceutrosomes, and a special physiological significance 

 has been attached to tliem. In the rods, one was figured by 

 Hensen years ago, but was apparently passed over without 

 comment. There can, I think, be little doubt that these must 

 also be regarded as so much chromatin escaping from the 

 nuclei. In the first place, they bear such a striking resem- 

 blance to similar bodies frequently seen v/ithin nuclei. Both 

 inside and outside of the nuclei, they are always surrounded 

 by a clear ring representing a fluid envelope. Within the nuclei 



