Johnson. — Nuclear Division 



PLATE III. 



Figs. 27-34 are all from the serosa. 



Fig. 27. A cell undergoing division by formation of a cell plate. The daughter 

 nuclei are still united by a connecting thread. The dotted line on the 

 left indicates the edge of the fragment of membrane in which this 

 cell occurs. From the serosa of an advanced embryo. X 304. 



Fig. 28. A cell divided by constriction, without the formation of a cell plate. The 

 nuclei have undergone degeneration. From the serosa of an advanced 

 embryo. X 150. 



Fig. 29. A cell, the nucleus of which has undergone tripartite division. From an 

 old serosa. X 150. 



Fig. 30. Nucleus of the same, more highly magnified. The chromatin is grouped 

 in granular masses. Two of the daughter nuclei are still united by 

 strands of the nuclear membrane. X 630l 



Figs. 31-32. Constricted nuclei from a young serosa. One of the daughter nuclei 

 of each is larger than its mate, and has itself become elongated and 

 constricted. X 304. 



Fig. 33. Quadrinucleate cell. The upper of the two original nuclei has divided 

 in a longitudinal, the lower in a transverse plane. Nucleus a still 

 shows a remnant of the connecting thread, and nucleus b retains the 

 conical form it had in division. Both nuclei have rotated 90° from 

 the plane of elongation. X 304. 



Fig. 34. Cell from tlie serosa of a far advanced embrj-o The nuclei have under- 

 gone extreme degeneration. Each nucleus is surrounded by a bright 

 ring, outside of which is a broad zone of a radiate structure, more 

 stainable than the rest of the cytoplasm. X 150. 



