CHAPTER VI 



REORGANIZATION 



At seemingly irregular intervals stentors form an oral primordium 

 which serves neither for division nor regeneration but merely 

 replaces oral structures already present. This has been called 

 reorganization or physiological regeneration. As these terms imply, 

 it has been supposed that this act is a necessary renewal of worn-out 

 organelles, but this is by no means certain and the real meaning of 

 the act is still to be ascertained. The problem of this peculiar 

 redifferentiation of the cell is not unique to Stentor. Reorganization 

 also occurs in the related Condylostoma (Tartar, 1957b) and 

 Bursaria (Lund, 1917), as well as in many other ciliates. 



The course of reorganization in coeruleus was well described 

 by its discoverer, Balbiani (1891a). To this description Schwartz 

 (1935) added many significant details in the most complete and 

 best illustrated account in the literature, and additional points 

 were contributed by others, as will be noted. 



1. The course of reorganization 



The first indication of reorganization is the beginning of an oral 

 primordium. Approximately at mid-body level below the mouth- 

 parts a splitting of pigmented stripes occurs as in division, 

 but multiplication of clear and granular stripes is not so extensive 

 (Fig. 20). The good reason for this is that a complete new adoral 

 field is not to be formed but only an addition to the old one. As 

 the primordium lengthens and develops, its anterior end meets 

 the old membranellar band at the point where the latter begins 

 to form the margin of the oral pouch. At stage 5 the original 

 mouthparts begin to dediflferentiate. Macronuclear beads start to 

 fuse and form a compact mass by stage 6, beginning renodulation 

 at stage 7. According to Weisz (1949a), some of the terminal nodes 

 may not fuse and if this occurs they break free. He also reported 

 that endoplasmic streaming carries the clumped nucleus as well 



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