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THE BIOLOGY OF STENTOR 



J. Development of a loop primordium. To a stage-3 divider 

 was grafted a stage-2 regeneration primordium. As shown in 

 first sketch, the host anlage is developed to stage 5 and the 

 implanted primordium extended to form two parallel memhra- 

 nellar bands separated by only a single stripe. The specimen 

 divided, with the loop primordium going to the proter, resorbing 

 one of the bands and forming no mouthparts but only a curl. 



K. Polarity in early stage-4 primordium. Mid-section was 

 reversed in situ. Parts did not rejoin, as when merely transected, 

 but developed separately. 



