Primary ontogenetic processes founded upon primary potencies may *imply* regulation, or more correctly, restitution in many cases: so it is, when fragments of the blastula form the whole organism, or when the mesenchyme cells of Echinus reach their normal final position by an attraction on the part of specific localities of the ectoderm in spite of a very abnormal original position enforced upon them by experiment. In these cases we speak of primary regulations or restitutions; disturbances are neutralised by the very nature of the process in question. We speak of secondary restitution whenever a disturbance of organisation is rectified by processes foreign to the realm of normality; and these abnormal lines of events are revealed to us in the first place by the activity of potencies which remain latent in ontogeny proper. We know already that a certain kind of secondary restitution has been discovered lately, very contradictory to the theoretical views of Weismann; the process of restoration being carried out not by any definite part of the disturbed organisation, but by all the single elements of it. The problem of the distribution of secondary potencies in these cases of so-called “re-differentiation” is to form our special study in the next chapter. In all other cases restoration processes start from specific localities; if they occur on the site of the wound which caused the disturbance, we speak of regeneration; if they occur at some distance from the wound, we call them adventitious processes. Besides these three types of processes of restitution there may be mentioned a fourth one, consisting in what is generally called compensatory hypertrophy; the most simple case of such a compensatory process is when one of a pair of organs, say a kidney, becomes larger after the other has been removed.[48] Finally, at least in plants, a change of the directive irritability, of so-called “geotropism” for instance, in certain parts may serve to restore other more important parts. [48] But real compensatory differentiation occurs in the cases of so-called “hypertypy” as first discovered by Przibram and afterwards studied by Zeleny: here the two organs of a pair show a different degree of differentiation. Whenever the more specialised organ is removed the less developed one assumes its form. Similar cases, which might simply be called “compensatory heterotypy,” are known in plants, though only relating to the actual fate of undifferentiated “Anlagen” in these organisms. A leaf may be formed out of the Anlage of a scale, if all the leaves are cut off, and so on.