2X0 Caholtnk McGii.i,, 



3. Orii^iii of Small from Lar^^e Nucleoli. 



Ill Klossia, according- to Schneider (1883) the small nucleoli 

 arise as portions of tlie inner substance of tlie larger nucleoli and 

 wander out through pores in the cortical substance of the latter. 

 Brauee (1891) and Floderus (1896) have observed para-nucleoli 

 budding off from the surface of the true nucleoli. 



4. Derivation of Chromatin from the Nucleolus. 



Hall (1893) in the ovum of Miis says that during- mitosis the 

 central granules of the nucleolus wander out and become the 

 chromosomes. Korschelt (1895) in the ovum of Ophryotrocha ob- 

 served the nucleolus gradually dissolving in the nuclear sap. He 

 believes that this substance helps to form the chromosomes. Auer- 

 bach (1896) in the spermatogonia of Palndina finds that during 

 mitosis the nucleolar substance becomes incorporated in the chromatin 

 elements. Guenther (1903) in Echinoderm eggs states that in the 

 resting cell all the chromatin is in the nucleolus. When preparing 

 for mitosis, the chromatin separates, either, as in Holothuriae, as a 

 segmented spireme, the segments of which later form the chromosomes, 

 or, as in Echinoidea. as the completely formed chromosomes. 



5. Discharge of Nucleolar Material from Resting 



N u c 1 e i. 



Ogata (1883) in human pancreas cells finds that the nucleolus 

 wanders out of the nucleus, becomes a "Nebenkern" and later changes 

 into the nucleus of a new cell. Will (1884) thinks that the larger 

 nucleoli of the amphibian germinal vesicle pass out into the cyto- 

 plasm and there become yolk-nuclei. MacCallum (1891) concludes 

 that in ova of Amphibia the peripheral nucleoli generate a substance 

 which diffuses first into the nucleus and from there into the cyto- 

 plasm; finally, it combines with the cytoplasm to form yolk. 

 Henneguy (1893) believes that the corpuscles of Balbiani in Verte- 

 brates are either parts of the nucleolus or the entire nucleolus which 

 passes through the nuclear wall into the cytoplasm. Montgomery 

 (1899) in Piscicola describes the nucleolus contracting in volume and 

 by so doing discharging all except one of its nucleoli into the cyto- 

 plasm. Hatai (1904) in the spinal ganglion cells of the rat figures 

 the nucleolus as passing entire through the nuclear membrane. In 

 the cytoplasm it breaks up to form Nissl bodies. As the Nissl 



