158 THE BIOLOGY OF STENTOR 



partners. For instance, this endoplasm, during primordium 

 formation and development, might be charged with an unusual 

 amount of RNA in support of the extensive synthesis which then 

 presumably occurs. But if it is the semi-solid ectoplasm which is 

 involved, the transmission would be more probably something 

 like an electrical excitation of a more novel character. Moreover, 

 the synchronization of developing anlagen without indication of 

 competition for substrates suggests that not one substance or 

 state of excitation is concerned but a series, paralleling the stages 

 in primordium development. 



If nourished stentors are continually undergoing structural 

 growth and not merely stretching or extending the distance 

 between their formed parts as seems evident in the case of the 

 lateral striping (see Fig. iia), how is this possible when during 

 the same period synthesis and morphogenesis in oral redifferentia- 

 tion is being so effectively inhibited that a stentor can even cause 

 the regression of the primordium of another stentor and even after 

 that anlage has been well-started ? Yet extensive nodal increase in 

 the macronucleus does seem to require the state of activation or its 

 final phases, since this increase occurs only during the last stages 

 of primordium development and it appears that reorganizers may 

 instigate anlagen formation in order to accomplish this nuclear 

 increase. Evidently the different parts of the pattern of cortical 

 differentiations, however, constitute a very precise responding 

 system in respect to growth ; and this is also indicated by specific 

 resorption of extra mouthparts or in a disproportionately long 

 membranellar band, when all other parts remain apparently 

 unaffected. 



In the resolution of such problems relating to cell states in 

 Stentor I think we may expect interesting discoveries which may 

 in turn prove relevant to cell differentiation in general. 



