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THE BIOLOGY OF STENTOR 



substance may travel along the tube-like internodal connections, 

 stopping between two nodes and growing into a new one. Weisz 

 (1949a) stated that extra nodes are thus interpolated whenever the 

 strand between two nodes measures approximately 2 nodal 

 diameters or more. Yet it should be emphasized that major nuclear 

 increases occur only following primordium formation in division, 

 regeneration, and reorganization. 



Fig. 80. Aspects of macronuclear nodulation in S. coeruleus, 



A. Diagram of two means by which single nodes appear to be 

 added: {x) by division and {y) by interpolation between nodes. 



B. When the clumped macronucleus of a stage-6 regenerator 

 is excised with a small amount of cytoplasm, the primordium 

 completes stomatogenesis and the nucleus attempts to renodulate 



though isolated and confined. 



C. When coalesced nucleus of a divider is sliced into several 

 times, the macronucleus is divided but fails to renodulate, doing 

 so only much later after regeneration is induced by excision of 



mouthparts without injury to the nucleus. 



I have found that when the clumped nucleus of a divider is 

 isolated into a small volume of cytoplasm it nevertheless attempts 

 to renodulate in spite of the confinement (Fig. 8ob). This suggests 

 that the impulse to nodulation is intrinsic with the nucleus itself 

 since the nuclear environment was so completely altered. Individual 

 nodes are very tough and resistant to cutting but the clumped 

 nucleus can easily be slashed through with a glass needle. In the 



