FUSION MASSES OF WHOLE STENTORS 



209 



doublet contract independently as Balbiani (1891b) first described. 

 Doublets generally show the single conical shape ending in one 

 holdfast, but there are two contractile vacuoles, two macronuclear 



Fig. 58. Conversion of doublets to singles. 



A. Doublet becomes single by removing one of the primor- 

 dium sites or major loci of stripe contrast. On reorganizing, both 

 sets of original mouthparts are resorbed and the excised l.s.c. is 



not reconstituted. 



B. Spontaneous conversion, in which one (x) of the two 

 original loci of stripe contrast disappears and the specimen 

 reorganizes singly, also achieving a single macronuclear chain. 



C. Isolated head end of doublet shows first a proportionate 

 shortening of the membranellar bands, then cutting out and 

 resorption of one of the mouths and obliteration of one primor- 

 dium site, becoming a normal stentor even without primordium 



formation. 



