It is a fact, that many species of the lower order of animals which once existed are now extinct. It has been asserted and denied, that fossil remains of man have been found, indicating that races which once existed have disappeared from the face of the earth. The pyramids are unfolding a wonderful history, embracing a period of forty-five hundred years, which the world of science receives as literally authentic, and admits, also, that fifty-four hundred years are _probably_ as correctly accounted for. The extinction of races is not at all improbable. At the present time, the aboriginal inhabitants of this continent seem to be surely undergoing gradual extinguishment! It, therefore, seems to be possible for a weaker race to deteriorate, and finally become extinct, unless the causes of their decadence can be discovered and remedied. All people are admonished to earnestly investigate the essential conditions necessary for their continuance, for the rise and fall of nations is in obedience to natural principles and operations. Viewed from this standpoint, it is possible that a careful study of the human temperaments and their relations to reproduction may be of greater moment than has hitherto been supposed, and a proper understanding of them may tend to avert that individual deterioration, which, if suffered to become general, would end in national disaster and the extinction of the race. Until recently, even naturalists believed that descendants were strictly like their parents in form and structure. Now it is known that the progeny may differ in both form and structure from the parent, and that these may produce others still more unlike their ancestry. But all these peculiar and incidental deviations finally return to the original form, showing that these changes have definite limits, and that the alterations observe a specific variableness, which is finally completed by its assuming again the original form. (See page 16, Figs. 2 and 3). _Reproduction_ may be _sexual_ or _non-sexual._ In some plants and animals it is non-sexual. The propagation of species is accomplished by buds. Thus the gardener grafts a new variety of fruit upon an old stock. The florist understands how to produce new varieties of flowers, and make them radiantly beautiful in their bright and glowing colors. The bud personates the species and produces after its kind. Some of the _annelides_, a division of articulate animals, characterized by an elongated body, formed of numerous rings or annular segments, multiply by spontaneous division. A new head is formed at intervals in certain segments of the body. (See Fig. 97).