290 



THE BIOLOGY OF STENTOR 



the conditions in Weisz's experiments were not optimal. Further- 

 more, Suzuki (1957) could find no evidence for differences in the 

 potentiality of parts of the nucleus in Blepharisma at any stage. 

 Above all, I was unable by similar experiments to confirm that a 

 regular and recurring difference develops between the serial nodes 

 of the nucleus (Tartar, 1957b). I tested five different races of 

 coeruleus and observed not only oral regeneration but also recon- 

 stitution of the nuclear chain from a single node and the capacity 

 of fragments to reproduce indefinitely in clones. For comparison 

 I studied Condylostomum magnum^ which is a very long ciliate 

 with mouthparts far to one end and a uniform chain nucleus 

 running the length of the body. If posterior nodes regularly 

 become depotentiated, the same should be manifested in this form 

 even more than in Stentor. It was found that even the single, 

 terminal posterior node in many cases or at least the last four 

 could support complete oral regeneration at any stage (Fig. 81). 

 In stentors (where this was tested) pre-fissional and pre-reorganiza- 

 tional fragments with only such nodes could give rise to viable 

 lines with normal chain nuclei. 



Fig. 81. Equivalence of macronuclear nodes in (A) Stentor 



coeruleus and (B) Condylostoma magnum. Tiny fragments of early 



dividers, carrying only a few of the most anterior or posterior 



nodes, are capable of regeneration and more. 



Evidently intranuclear differentiation is neither necessary for 

 nor the consequence of cytoplasmic differentiation in ciliates. We 

 can therefore return with confidence to the old dictum that any 



