ACTIVATION AND INHIBITION: ORAL PRIMORDIUM I39 



about four hours between inducement of regeneration and first 

 appearance of the primordium is probably occupied, not by 

 developing an anarchic field or other assemblage of formed 

 materials for the anlage but in transforming the cell from a state 

 of inhibition to one of activation (Tartar, 1958b). 



In the rapid re-formation of anlagen in regenerators minus 

 primordium sectors the primordia themselves are normal and lead 

 to successful regeneration, but their manner of appearance is un- 

 usual. As shown in Fig. 34B, the line of heal simply reopens and an 

 anlage appears in the rift. Apparently there is no time for con- 

 comitant stripe multiplication in the presumptive frontal field, 

 and the primordium simply cuts out and carries forward some of 

 the relatively wide striping on its right side. The frontal field is 

 correspondingly abbreviated and reorganization therefore often 

 follows. 



A similar appearance is also found in induced reorganization. 

 If a stage-3 regenerator is grafted to a smaller non-diflFerentiation 

 cell the latter exerts an initial influence by causing the arrest or 

 even partial regression of the regenerator's anlage, though later 

 the regenerator is dominant and induces normal primordium 

 formation, with stripe multipHcation, in the partner which then 

 reorganizes simultaneously (Fig. 3 5 a). But when a stage-4 

 regenerator is used no transient regression of the original anlage 

 occurs, and the induced primordium may be forced to appear so 

 rapidly that there is neither stripe multiplication nor normal 

 growth in length of the anlage (b). As indicated in the first example, 

 the impression is unmistakable that in mis-matched grafts there is a 

 contest and conflict between primordium activation and inhibition, 

 the flnal outcome of which is only decided after some time. 

 Figure 35c illustrates a case in which an incipient regenerator was 

 grafted to a small non-diflferentiating partner: a regeneration 

 primordium soon appeared and an anlage was induced in the other 

 component, then regression of both primordia occurred, after 

 which both were revived and regeneration-reorganization went 

 to completion. If in balance, with the forces of inhibition apparently 

 equalling those of activation, neither resorption nor development 

 occurs ; the primordium is not merely arrested but seems abortive 

 as it takes on a crumpled appearance, and so the graft complex 

 remains for a half-day or more until an entirely new start is made 



