The situation should be clarified by an analogy: After assigning the north and south pole of a globe, the equatorial zone and a hot spot thereupon can be defined. This, however, would require a competition along the whole equatorial zone if only a single spot on the equator should be allowed. Since an inhibitor would be also diluted into non-equatorial regions, the formation of a second spot at the opposite position is hardly avoidable. To solve this problem it is proposed that shortly after the definition of the south pole, a second special region is generated that is eccentric to the south pole (like New Zeeland). In this way the symmetry is broken. This can be done at a much earlier stage, before the formation of the equatorial zone is finished. The asymmetry generated in this way restrict the possible region at which later the equatorial spot can emerge.
Involved in the generation of this eccentric Nieuwkoop center are molecules such as WNT, ß-catenin, Tcf3
As mentioned, Nieuwkoop  observed that the notochord and the neural tube could also form in aggregates, i.e., after waiving out the asymmetric localization of determinants. Together with the function of the Nieuwkoop center discussed above, this suggests that the ß-catenin – siamois
pathway is not only involved in bringing pre-localized determinants to function but is also part of a real pattern forming system. This is supported by the experimental findings that siamois
has a feedback on its own activation  and that an ectopic activation can cause a complete secondary axis . As further confirmation of the model, it would be very interesting to learn whether siamois
activation or other elements of the WNT pathway also become locally active in Nieuwkoop aggregates. It is remarkable that least the first three molecules are also involved in the head signaling of hydra
. Thus, the formation of primary organizing regions is seems to be under control of universally used molecules.