226 



BIOLOGY OF THE PROTOZOA 



of the presence or absence of a micronucleus, a fact indicating a 

 change in organization with advancing age (Fig. 108, 5). 



The fate of the motorium and of the coordinating fibrils at divi- 

 sion is still unknown, but the prediction may be made that, like 

 other kinetic elements, it also divides during the reorganization 



Fig. 108. — Uroyiychia transfuga, merotomy and regeneration. 1, cell immediately 

 after division, cut as indicated; 2, fragment ^ of 1, three days after the operation; 

 no regeneration; 3, cell cut five hours after division; 4, fragment A of 3, three days 

 after operation, no regeneration ; 5, cell cut at beginning of division as indicated into 

 fragments A, B, and C; A', B', C", fragments A, B and C, twenty-four hours after 

 the operation; fragment A regenerated into a normal but emicronucleate individual 

 (A'); B, C divided in the original di\-ision plane forming a normal individual (C') and 

 a minute but normal individual {B') . (After Calkins.) 



process. It is a significant fact that the peristome and the peri- 

 stomial organs appear first in the more s})ecialized anterior half of 

 the ciliate cell, and from this position gradually shift to the region 

 immediately posterior to the division zone (Fig. 105). In VorticeUa 

 according to Biitschli (1S88) after Fabre, the peristome and adoral 

 zones are reversed in the daughter cells. 



