230 THE BIOLOGY OF STENTOR 



Division occurred while the stripes were interpenetrating and the 

 fission Hne did not follow the suture but cut indiscriminately 

 across fine and broad striping, following a course which may be 

 called typical (d). The latter, with similar cases, shows that abnormal 

 disharmonies and discontinuities in the lateral striping do not 

 preclude division and suggests that the fission line is determined 

 by some agent other than the lateral stripes themselves. Thus the 

 same subcortical forces which cause predivision of the carbo- 

 hydrate reserves in the neat manner already described may impose 

 a severance of the striping lying exterior to them regardless of the 

 nature or disposition of that striping. 



Yet the most interesting questions concern how the highly 

 structured ectoplasm can permit stripe areas to slip by each other, 

 as well as the bearing of stripe extensions in limited places on the 

 control of growth throughout the cortex. Moreover, it appears that 

 races of coeruleus vary in the ease with which stripes interpenetrate 

 after this operation, specimens of one strain remaining as grafted (e) 

 long after those of another had formed doublets. 



Uhlig (1959, and unpublished) has developed this type of 

 experiment much further, by transecting coeruleus at different levels 

 before rotating the two parts. He substantiated that when the cut 

 passes through the place of origin of the primordium producing 

 approximately equal halves for rotation, the anterior striping is 

 generally resorbed as the posterior stripes extend and take over.* 

 When a posterior cut produces an anterior component about four 

 times the size of the posterior, anterior striping now predominates 

 and extends posteriorly, replacing the original tail-pole striping 

 which is resorbed. The case shown in Fig. 66f confirms this 

 finding. A dividing stentor was transected across the oral end of the 

 division primordium and the smaller posterior part rotated on the 

 larger. The tip of the anlage was then resorbed ; the larger portion 

 continued development and led to reorganization as the original 

 posterior striping gradually disappeared. But these cases were not 

 uniform and sometimes there was an interpenetration of stripes. 

 Therefore it appears that in these grafts there is a delicate balance 

 between the two systems which may be tripped to favor the 



* Uhlig (i960) claims that resorption of the anterior striping proceeds 

 from the anterior ends of this striping and not from the suture. 



