A particular observation made by Goethe in this respect is of interest for methodological reasons. In the introduction to his treatise Metamorphosis of Plants, when referring to the regressive metamorphosis of stamens into petals as an example of an irregular metamorphosis, he remarks that 'experiences of this kind of metamorphosis will enable us to disclose what is hidden from us in the regular way of development, and to see clearly and visibly what we should otherwise only be able to infer'. In this remark Goethe expresses a truth that is valid in many spheres of life, both human and natural. It is frequently a pathological aberration in an organic entity that allows us to see in physical appearance things that do not come outwardly to the fore in the more balanced condition of normal development, although they are equally part of the regular organic process.