Higher organisms have, as the rule, the geometry of a long stretched cylinder. An organizing region appropriate to generate the pattern for the mediolateral or dorsoventral axis must have the geometry of a long extended but narrow stripe. For many systems it has been shown that the midline can regenerate after removal [5-7], showing that the midline organizer has self-regulatory properties. What type of molecular interactions would be able to generate a region of high concentration that has a stripe-like geometry?
As shown, stripe formation
can be accomplished by a pattern-forming reaction in which the self-enhancement saturates. On its own, however, such a stripe-forming system is still insufficient to generate a solitary straight stripe. Upon initiation by random fluctuations, somewhat meandering stripes would be formed that may bifurcate. The width of the stripes and the inter-stripe regions are of the same order, reminiscent of the ocular dominance columns, patterns on zebras or on some tropical fishes. The problem of multiple stripes cannot be circumvented by a strengthening of the lateral inhibition since this would lead to a decay of the stripe into individual patches.