Johnson. — Nuclear DivisioQ. 



PLATE I. 



Fig. 1, Five ceils of the serosa, two of tlieni covered by the amnion, which is 

 omitted from tlie rest of the figure for the salce of clearness, am., 

 amnion ; sr., serosa. X 150. 



Fig. 2. Section through the embryonal membranes and ovarian capsule. The 

 fibrous appearance of the ovarian capsule is due to the presence of 

 muscle fibres and connective tissue. The boundary line between 

 amnion and serosa is visible only in the vicinity of the amniotic 

 nuclei, e'th. fol., epithelium of ovarian capsule (when the plates were 

 engraved I still took this to be the follicular epithelium, hence the 

 error in the abbreviation); n/. /6/., nucleus of capsular epithelium; 

 nl. sr., nucleus of serosa ; nl. am., nucleus of amnion. X 630. 



Figs. 3-15 are all from the serosa. 



Fig. 3. Very small, binucleate cell. X 130. 



Figs. 4-10. Nuclei at diflferent stages of division, vac, vacuole ; x, new nuclear 

 wall within the old one. X 550. 



Fig. 11. Two cells produced by division of a binucleate cell. X 130. 



Fig. 12. Ceil from the serosa of a young embryo, with dividing nucleus ; the axis 

 of elongation corresponds with the short axis of the cell. X 130. 



Fig. 13. Cell from serosa of a young embryo, with nucleus unequally divided and 

 daughter nuclei eccentric in position. X 130. 



