REPRODUCTION 



147 



the macronucleus of Nyctotherus ovalis probably produce smaller 

 spherules in their alveoli (Fig. 3). 



When the macronucleus is elongated as in Spirostomum, Stentor. 

 Euplotes, etc., the nucleus becomes condensed into a rounded form 

 prior to its division. During the "shortening period" of the elongated 

 macronuclei prior to division, there appear 1-3 characteristic zones 

 which have been called by various names, such as nuclear clefts, 

 reconstruction bands, reorganization bands, etc. In Euplotes patella 



Fig. 53. The solation of chromatin during the macronuclear division of 

 Chilodonella cucullulus, as demonstrated by Feulgen's nucleal reaction, 

 Xl800(Reichenow). 



(E. eury stomas) , Turner (1930) observed prior to division of the 

 macronucleus a reorganization band consisting of a faintly staining 

 zone ("reconstruction plane") and a deeply staining zone ("solution 

 plane"), appears at each end of the nucleus (Fig. 54, a) and as each 

 moves toward the center, a more chromatinic area is left behind 

 (b-d). The two bands finally meet in the center and the nucleus as- 

 sumes an ovoid form. This is followed by a simple division into two. 

 In the T-shaped macronucleus of E. woodruffi, according to Pierson 

 (1943), a reorganization band appears first in the right arm and the 

 posterior tip of the stem of the nucleus. When the anterior band 

 reaches the junction of the arm and stem, it splits into two, one part 



