LOCALIZATION OF NEW AXES IN C( K Y M < iKIMI A. 477 



obliterated the polarity is obliterated, so far as can be determined. 



It has been shown for many forms, both plant and animal, that 

 buds originate as gradients of this sort, resulting merely from the 

 localization of an active region which is not sharply marked off 

 from its surroundings but shows a gradient of decreasing activity 

 from a central region toward the periphery. In consequence of 

 differential growth, which itself results from the existence of this 

 gradient, the radial gradient becomes an apicobasal gradient and 

 a polar axis. There is no evidence to indicate that a polar axis 

 is primarily anything more than such a dynamic differential with 

 its structural protoplasmic correlates, or that differentiation along 

 an axis requires anything more for its initiation than the quanti- 

 tative differences at different levels of such a gradient. 



The development of basal instead of apical structures from a 

 lateral injury under inhibiting conditions is in complete agreement 

 with the results of other experiments. It has been shown that the 

 basal region of Corymorpha represents a secondary gradient which 

 originates at the low end of the primary gradient (Child and Hy- 

 man, '26; Child, '260). The high end of this secondary gradient, 

 so long as it persists, is the basal tip and the slender modified 

 stolons which constitute the holdfasts develop as lateral buds along 

 this secondary gradient. These stolons show extremely rapid 

 growth, but they originate only in regions of relatively low activity. 

 When the activity of the region of lateral injury is decreased to 

 a certain degree by inhibiting factors, the conditions must become 

 more or less similar to those existing at the lower end of the pri- 

 mary gradient, and the lateral injury, like the lower end of the 

 primary gradient, develops as a basal region. Whether a single 

 basal outgrowth bearing stolon buds, or merely the stolon buds 

 appear probably depends on various factors, e.g., the degree of 

 inhibition, the presence or absence of a definite growth region, etc. 

 If a single general basal outgrowth arises the further development 

 of the basal gradient and basal region follows in the same way as 

 the development of the hydranth-stem gradient and region. Even 

 if the central growth area resulting from the injury is not suffi- 

 ciently well defined to determine a single general basal outgrowth, 

 new stolon buds may be determined in relation to the entodermal 

 canals or parts of canals in the injured region. Since the canals 



