If you consider the matter you will realize that the lower the life form the more capable it is of regenerating a lost part. Passing downward from lizards and worms we find that the vegetable kingdom provides an even better example of a form of regeneration, for if we remove a limb of a tree (branch) another will grow to replace it. However, even with human beings there is a form of regeneration; for instance, if you lose a piece of skin through an abrasion new skin will grow to replace it, but perhaps this cannot be considered true regeneration as you mean it. The answer to your question lies in the fact that as life progresses in physical manifestation it becomes more individualized in matter. Likewise the etheric archetype evolves in its own dimension. The dividing line between the life forms that can regenerate and those that cannot is that which divides the mammals and other warm blooded creatures from lesser life forms. Below this line regeneration is possible, above it it is not. Warm blooded creatures grow and develop according to an etheric archetype which reproduces them in the physical and this archetype has individuality, complete in the case of human beings, less and less complete as the life form descends towards the barrier just mentioned. So a human being develops in accordance with an etheric pattern which remains perfect irrespective of what modifications are made to its physical counterpart. The higher the life form the less important becomes the physical manifestation in relation to the etheric, more spiritual counterpart. Lesser forms of life, below the dividing line, do not have individual archetypes, there is a single pattern for all and consequently physical events do not have the same individualizing impact. The higher the life form the greater its capacity for experiencing the modifying effects of
life. The lower the life form the less benefit it will derive from the experiences of life and so life, as expressed in physical form, tends to counteract any modifications caused by its vicissitudes. A worm, for instance, has practically no ability to choose, being limited in all ways, even its movements from sunlight to darkness, from dryness to humidity, are purely reflex ones. Therefore, whatever happens to it, as for example if it gets cut by a spade, is meaningless to it in terms of development and so there is a tendency for the cells to multiply along the lines of the related forcefield of the original pattern and thus reproduce the missing part. If human beings were able to regenerate a missing part at will it would remove from them a considerable amount of personal responsibility. Imagine how careless people would be if they knew they could regenerate missing legs or arms! In fact the situation would become chaotic. One of the lessons we are here to learn is personal responsibility, others are prudence and orderliness. All these would be nullified were the same laws to apply to humans as to lizards, for instance.