18 E. J. LUND 



2. Encystment follows complete disappearance of the anlage 

 of the gullet, but polarity of the cell is probably not lost. During 

 cell division the anlage of the gullet remains and from it a new 

 gullet is formed by differentiation. The extent of cytoplasmic 

 dedifferentiation varies with the degree of mechanical injury and 

 size of the lost part. 



3. Heteromorphic cells may arise from either normal indi- 

 viduals, anterior, posterior, right, or left halves. In every case 

 differentiation took place in a cell or part of a cell which was first 

 dedifferentiated. 



4. Reversal of polarity of one of the members of a heteromorph 

 may occur as a result of dedifferentiation of that member. Re- 

 versal of polarity and dedifferentiation in all observed hetero- 

 morphs took place in the smaller and weaker member. Hetero- 

 polarity may occur with very little other evidence of its exist- 

 ence than the direction of beat of the cilia. 



5. The morphogenetic processes in Bursaria and probably in 

 many other cells are reversible (defined page 13) in their nature, 

 One phase of this reversible system i$ represented by differentia- 

 tion, the other by dedifferentiation. 



6. Evidence for the existence of a specific type of physical- 

 chemical mechanism for dedifferentiation similar in its action to 

 the mechanism of autolysis, is given in the text. 



7. The reversible morphogenetic processes described for Bur- 

 saria concern only changes in relatively unstable, secondary 

 structures in the cell and do not visibly affect the more stable 

 nuclear mechanism. 



