Let us apply this thought to the development of a species; although what is true of the species will generally be true of the individual also, for the development of the two is, in the main, parallel.  In the animal all functions are to a certain extent productive, and all directly or indirectly prospective.  When we examine the sequence of functions we cannot but notice how largely their value is prospective.  As long as a lower function is rising to supremacy in the animal, it appears to be retained purely for its productive value; thus digestion in hydra or gastraea.  But after a time animals appeared which had some muscle and nerve.  And, by the process of natural selection, those animals which used digestion as an end for its productive value became food for, and gave place to, those using it as a means of supporting muscle and nerve of greater prospective value.  And similarly, those animals which used muscle, or even mind, productively gave place to others using these prospectively.

In other words, the functions and capacities of any animal, the extent of its conformity to environment, may be regarded as its capital.  The animal may use this capital productively or prospectively.  It may spend its income, and more too; it may increase its capital.  Now social capital will always fall sooner or later to those communities whose members use it most prospectively, who are willing to forego, to quite an extent, present enjoyment, and look for future return.  The same is true of all development.  Sessile forms and mollusks, and, in a less degree, crabs and reptiles, worked for immediate return.  They are like extravagant heirs who draw on their capital and sooner or later come to poverty.  The primitive vertebrate, the mammal, and the other ancestors of man used their capital prospectively, and it increased, as if at compound interest.

The spendthrift appears at first sight to have the greatest enjoyment in life, the rising business man works hard and foregoes much.  I believe that the latter is really by far the happier of the two.  But, if you can spend only a day or two in a city, and your examination is superficial, you may easily make the mistake of considering the spendthrift as the most successful man in the community.  So, in our brief visit to the world in times past, we picked out the crab, the reptile, and the carnivore as its rising members.

Once more, capital can be spent very quickly; to use it prospectively requires time.  This is a truism; but it does no harm to call attention to truisms which have been neglected.  Organs and powers of great prospective value are slow and difficult of development.  If their increase is to be at all rapid, they must start early.  If their development and culture is deferred, there will be little or no advance, but probably degeneration.  Extravagance grows rapidly and soon becomes irresistible; habits of saving must be formed early.  The same is true of the development of all other virtues.