from being in any way an abnormal phase of living action, it is seen to be as natural a process for living beings to retrogress—wholly, as we have seen in some cases, or partly, in others—as it is for them to develop and advance. And what is thus undoubtedly true of the individual man or other animal is no less so of the race. "Buried civilizations" are by no means unknown; extinct culture is an archæological fact; the decline and fall of nations are matters of history. May not these things be likewise explained as a part of that wide theory of life which regards even the highest interests of man as lying within the operation and sway of causes which mold his physical organization? If this notion be accepted, then is the idea of degeneration as a normal phase of life rendered still more feasible and plain. Reaching to the individual and to the species as well; extending and including in its scope the lowly organized as well as the higher being; affecting one group or class lightly, and influencing another wellnigh to the complete exclusion of progress, we find degeneration and retrogression to be numbered among the stern realities of existence. And no less clearly and forcibly may we trace the truly natural place of degeneration in our own physical history: since, as physiology teaches and daily experience declares, not an action is wrought or a thought conceived without the presence of change and decay of tissue a process this which, limited in early life by progressive growth and by development, at last comes in our latter days to assume the reins of government, and in time to dissipate our energy and substance into the nothingness of physical and corporate extinction.
The philosophy of biology, however, may, in conclusion, be found to point out to us that the subject of degeneration, while treating of a powerful factor in modifying the living form, yet possesses a favorable aspect in relation to progress and evolution. High authority in matters biological may be found for the statement that degeneration is really a result of progress, that it is dependent on high development, and that, while it simplifies the living being, "it produces the same effect as differentiation, for it leads to variety in form." Thus there is a kind of evolution and progress inseparable even from degeneration itself. For the retrogression may in itself lead to variety and change, and in due time such variety may be the starting-point of new and higher developments. So, likewise, we are reminded that reduction and degeneration of some parts may proceed contemporaneously with the higher development of others, with the total result of perfecting the organism and of evolving a higher type of structure. The degeneration of a frog's tail is in reality a feature of its higher type as compared with its tailed friends, the newts and salamanders. The disappearance and reduction of the tail which the young crab possesses is a chief reason why we esteem the crab, whose body is all head and chest, a higher animal than the lobster or prawn, with head, chest, and tail complete. The degeneration of the "outside" gills of the Alpine
