350 S. SAGUCHI 



exhibits one or two spherical nucleoli, reddish in color, and nu- 

 merous blue-stained chromatin granules, which, connected by 

 faintly stained, fine threads, form the so-called 'chromatin net- 

 work.' And the chromatin granules are, on the one hand, 

 closely applied to the surface of the nucleolus and are fused to- 

 gether so as to envelop the latter more or less completely; thus 

 forming what is usually called 'chromatin shell' (figs. 9, 12, 13, 

 22, 23, etc.), which seems to have been noticed by Ogata ('83), 

 Mouret ('95), and Arnold ('12) in the nucleus of the pancreatic 

 cell. Owing to the presence of this chromatin shell, it often 

 happens that in tangential view the nucleolus shows no char- 

 acteristic staining reactions, but stains blue like a chromatin 

 mass, as noticed by Arnold. The chromatin granules are, on 

 the other hand, applied upon the inner surface of the nuclear 

 membrane which appears, in cross-sections of the nucleus, as a 

 relatively thick basophilic line. The basophily of the nuclear 

 membrane is due to the extremely thin chromatin layer, which, 

 in surface view, reveals a delicate, faintly staining network. 



The chromatin substance of the nucleus is not only accumu- 

 lated, as above described, in the form of granules, but also in the 

 form of irregularly curved cords. These chromatin granules and 

 cords are not homogeneous, but exhibit, in various fixations and 

 stainings, a thin, deeply staining cortex and a faintly staining 

 main-mass, which suggests that the two parts are perhaps dif- 

 ferent in composition from each other (figs. 22, 25, 30). 



2. Nucleoli and nucleolar corpuscles. Most of the nuclei have 

 only one nucleolus; beside this there may exist several smaller 

 nucleoli; the larger one is then named 'main-nucleolus' and the 

 smaller ones are 'side-nucleoli.' There are also a number of 

 nucleolar corpuscles in the nucleus. 



a. Main-nucleolus. The main-nucleolus is, in most cases, of 

 spherical form with an even contour, but sometimes oval, round- 

 ish triangular or polygonal in form. In the vast majority of cases 

 it is single in number, but it sometimes happens that two, three, 

 or four nucleoli of nearly equal size are seen in the nucleus (figs. 

 4, 23, 37) ; they are possibly formed by a division which is ef- 

 fected not by the scission, but by the stretching out of the nucleo- 



