That a very close relation exists between the process of physiological regeneration and restorative regeneration will be sufficiently evident from the preceding illustrations. We do not gain any insight into either of the processes, so far as I can see, by deriving the one from the other, for the process of restorative regeneration may be, in point of time, as old as that of physiological regeneration. This does not mean, of course, that the same factors may not be present in both cases. So similar are the two processes that several naturalists have attempted to show how the process of restorative regeneration has been derived from physiological regeneration. Barfurth, recognizing the resemblance between the two processes, speaks of restorative regeneration as a modification of physiological regeneration, and Weismann also supports this point of view. He says: “Physiological and pathological regeneration obviously depend on the same causes, and often pass one into the other, so that no real line of demarcation can be drawn between them. We nevertheless find that in those animals in which the power of regeneration is extremely great physiologically, it is very slight pathologically. This proves that a slight power of pathological regeneration cannot possibly depend on a general regenerative force present within the organism, but rather that this power can be provided in those parts of the body which require a continual, periodic regeneration; in other words, the regenerative power of a part depends on adaptation.” It is, I think, erroneous to state “that in those animals in which the power of regeneration is extremely great physiologically, it is very slight pathologically.” All that we are justified in concluding from the evidence is that in some cases in which physiological regeneration takes place, as in the vertebrates, pathological (restorative) regeneration may not be well developed; but even in these forms restorative regeneration is certainly present, and present especially in internal organs, as in the salivary gland, in the liver, and in the eye, which are little exposed to injury. How far physiological regeneration takes place in the tissues of the lower animals we do not know at present, except in a few cases, but far from supposing it to be absent, it may be as well developed as in higher forms. Weismann’s further conclusion, that because in some animals physiological regeneration is very great and restorative regeneration very slight, therefore the latter cannot “depend on a general regenerative force within the organism,” is, I think, quite beside the mark. In this connection we should not fail to notice a difference between these two regenerative processes that several writers have also called attention to, viz. that the power of cell-multiplication and the formation of new cells in each kind of tissue does not carry with it the power of restorative or even of physiological regeneration, in cases