330 EXPLANATION OF THE PLATES. 



cell-membrane, has formed a new one, somewhat removed 

 from the green internal cell at one side. 



Fig. 18. The cell- membrane thrown off by splitting 

 into four pieces, with simultaneous division of the cell 

 into two daughter-cells. 



Fig. 19. As in fig. 18 ; but the two new t cells have 

 already become coated with cell-membrane. 



Fig. 20. The same; but the detached cell-membrane 

 split only into two parts. 



Fig. 21. The detached cell-membrane has broken up 

 into four portions, the internal cell has become trans- 

 formed by double halving into a group of four decus- 

 sating cells. 



Fig. 22. The same; but the cells have already 

 separated and become coated with new cell-membrane. 



