Mutual competition of nearby organizing regionsThe induction of new organizing regions by implantation of tissue fragments derived from the endogenous organizing region has been investigated in the chick  (Khaner and Eyal-Giladi, 1989) and extensively in hydra [2,3]. In general, implantation of such tissue at a distance from an existing organizer can be successful, while a more proximal implantation may not. Removal of the endogenous organizing region greatly enhances the probability to form a new organizing region. This behavior is a straightforward consequence of the general pattern forming mechanism proposed, as demonstrated by the following simulations:
Unspecific inductionOne of the problems in the early search for molecules involved in organizer formation was that very unspecific manipulations, such as implantation of denatured tissue or injury turned out to be sufficient to trigger the formation of a secondary embryonic axis. Waddington et al.  proposed that this non-specificity results from the removal of an inhibitor. The tendency for unspecific induction is species-dependent. It is high in Triturus, the model system most studied in the early days but is low in Xenopus.