148 
Transactions of the Society. 
F. During late Blastula and Gastrula Stages. 
1. An oxyphil staining nucleolus is present in all cells (figs. 16-22). 
2. Binucleate cells have been observed in early blastula stages (fig. 17). 
In some binucleate cells each nucleus has a nucleolus ; in others, a single 
large nucleolus is present inside the larger nucleus (fig. 18a). 
3. At each cell-division, the nucleolus disappears at the time when the 
chromosomes are reforming, and it makes its appearance again as a small 
oxyphil staining body amongst the chromosomes at late telophase (figs. 16 
and 17). 
4. Mesoderm cells arising in the gastrula, are characterized by the 
oxyphility of their cytoplasm, and the great activity of their nucleoli, 
which usually attain a considerable size, and often are seen fragmenting 
(figs. 19, 20, 21). 
G. In the Larval and Adult Stages. 
3. During the early gastrula stage, the endoderm cells contain a small 
nucleolus, and numerous small vacuoles in their cytoplasm (fig. 22). In the 
larva stage, however, such cells increase enormously in size, the vacuoles 
run together to form a few large ones, and the nucleolus enlarges considerably 
(fig. 23). 
2. Actively growing cells are characterized by their large nucleoli, and 
by the fragmentation and division of the same (figs. 19, 25, 26). 
3. In the adult, nucleoli of cells undergoing active metabolism are rela- 
tively large, those in “ resting ” conditions relatively small (figs. 27, 28). 
H. Nucleolar Extrusions. 
1. Extrusions of oxyphil staining nucleolar substances occur during 
oogenesis (figs. 2-6). 
2. Reasons have been advanced for believing that similar extrusions of 
nucleolar material occur in rare cases during development, and also in cells 
of the adult during conditions of great metabolic activity (figs. 19, 21, 22, 
24-26, and 28). 
Bibliography. 
1. Adami, J. G. — A Discussion on the Physiology and Pathology of the 
Nucleus. Brit. Med. Jour., 22nd Dec., 1906. 
2. Agar, W. E. — Cytology, with Special Reference to the Metazoan 
Nucleus. Macmillan (1920). 
3. Balbiani, E. G. — Sur les mouvements qui se manifestent dans la tache 
germinative chez quelques animaux. Compt. Rend, de la Soc. Biol. 
Paris, Ser. 4, 1 (1864). 
4. Boveri, T. — Uber Entwickelung und Yerwandtschatfsbeziehungen der 
Actinien. A. Zeit. wiss. Zool. Bd. 49 (1890). 
5. Carleton, H. M. — Observations on the Intranuclear Body in Columnar 
Epithelium Cells of the Intestine. Q.J.M.S., vol. 64 (1920). 
6. Chun, C. — Die canarischen Siphonophoren in monographischen Dar- 
stellu'ngen. Abh. Sene. Nat. Ges. Frankf. Bd. 16 (1891). 
7. Conklin, E. G. — Cell Size and Nuclear Size. Jour, of Expt. Zool., j 
vol. 12 (1912). 
8. Danchakoff, V. — Studies on Cell Division and Cell Differentiation. 
Jour, of Morph., vol. 27 (1916). 
9. Dobell, C. Clifford. — Chromidia and the Binuclearity Hypothesis : a 
Review and a Criticism. Q.J.M.S., vol. 53 (1909). 
10. Duesberg, J. — Plastosomen,“ Apparato reticolare interno,” und Chromi- 
dialapparat, Ergeb. der Anat. u. Entwickl., Bd. xx. 
“ Recherches cytologiques sur la fecondation des Ascidiens et sur 
leur developpement.” Contributions to Embryology, vol. iii, 
Nos. 7, 8, 9 (1915). 
