In the animal kingdom it is chiefly and almost solely the phenomena of regeneration proper which offer typical instances of our systems, since adventitious restitution, though occurring for instance in the restitution of the lens of vertebrates from the iris, and though connected also with the events in regeneration proper,[126] is of but secondary importance in animal restitution, at least, if compared with restitution in plants. If we study the regeneration of a leg in the common newt, we find that it may take place from every section, the point of amputation being quite at our choice. Without regarding here the exact order of the regeneration phenomena, which is almost unknown at present, we in any case can say without any doubt that the line of consecutive possible cross-sections forms a complex-morphogenetic system, as every one of them is able to give rise to a complex organ, viz. the foot and part of the leg. It is an open question whether this complex system is to be called “equipotential” or not. It indeed seems to be inequipotential at the first glance, for each single section has to form a different organogenetic totality, namely, always that specific totality which had been cut off; but if we assume hypothetically that the real “Anlage” which is produced immediately by the cells of the wounded surface is the very same for all of them, and that it is the actual state of organisation which determines to what result this Anlage is to lead,[127] we may say that the series of consecutive cross-sections of a newt’s leg does form a morphogenetic system of the complex-equipotential type, promoting secondary regulations of form. [126] The “regeneration” of the brain of annelids for instance is far better regarded as an adventitious formation than as regeneration proper: nothing indeed goes on here at the locality of the wound; a new brain is formed out of the ectoderm at a certain distance from it. [127] A full “analytical theory of regeneration” has been developed elsewhere (*Organ. Regul.* p. 44, etc.). I can only mention here that many different problems have to be studied by such a theory. The formation of the “Anlage” out of the body and the differentiation of it into the completely formed results of regeneration are two of them. The former embraces the question about the potencies not only of the regenerating body but of the elements of the Anlage also; the latter has to deal with the specific order of the single acts of regenerative processes.