Nature contains no sharply drawn lines.  Plants are different from animals; but there are animals so low down in the scale of life that it is difficult to distinguish them from plants.  Pigeons are distinct from pheasants, but the line at which the one species ends and the other begins is difficult to draw.  This fact seems to invite some theory of one form changing into other.  Accordingly the evolutionist explains the working of the process which he asserts to be sufficient to produce all the various forms of life in our globe.

After stating this more in detail than we have previously done, we shall be in a better position to judge if the process (which in the main we have no desire to deny or even to question) can dispense with guidance and the fixing of certain lines and limits within which, and of certain types towards which, the development proceeds.  That is our point.

It is hardly necessary to illustrate the enormous destruction of life which goes on in the world.  Even among the human race, the percentage of infants that die in the first months of their life is very large.  But in the lower forms of life it is truly enormous.  Only consider the myriads of insects that perish from hunger or accident, and from the preying of one species on another.  If it were not so, the world would be overrun by plagues of mice, of birds, of insects of all kinds, and indeed by creatures of every grade.  The term “struggle for existence” is, then, not an inapt one.  All forms of living creatures have to contend with enemies which seek to prey upon or to destroy them, with the difficulty of obtaining food, and with what I may call the chances of nature—­cold, storms, floods, disease, and so forth.

Now, it is obvious that if some creatures of a given kind possess some accidental peculiarity or modification in their formation which gives them (in one way or another) an advantage over their fellows, these improved specimens are likely to survive, and, surviving, to have offspring.

It is this perpetuation of advantageous changes, originally induced by the circumstances of environment, that is indicated by the term “natural selection.”  Nature chooses out the form best suited to the circumstances which surround it, and this form lives while the others die out.  And this form goes on improving by slow successive changes, which make it more and more fit for the continually changing circumstances of its life.

Subordinate also to this natural selection is the principle that bright colour and other special qualities may be developed in the males of a race, because individuals with such advantages are more attractive, and therefore more easily find mates, than dull-coloured or otherwise less attractive individuals.