Probability aspects of supernumerary production in the regenerating limbs of the axolotl, Ambystoma mexicanum.

The applicability of deterministic models, and in particular the polar co-ordinate model of French, Bryant & Bryant (1976), to the regenerative process has been investigated by performing ipsilateral blastemal rotations of varying angle on the fore and hind limbs of the axolotl. The results show that the frequency of supernumerary production rises with increasing angle to reach a peak at 180 degree and then falls off more rapidly, giving rise to an asymmetric distribution curve. The position of supernumerary outgrowth als suggests a probabilistic event, there being no consistent relationship between this parameter and the angle of rotation. The polar co-ordinate model is incapable of explaining these results and the work suggests that the determinism of current regeneration models may have to be abandoned in favour of a more stochastic theory.