Page:Popular Science Monthly Volume 12.djvu/194

182 same way that the infant passes from birth to manhood. That was, I say, the vulgar opinion, but, in laying before our eyes the development of the individual, God has given us a revelation of the course of life by the world.

The evolutionary history of animals establishes that there is not this homogeneousness of development, but that the higher pass through the forms of the lower; that the mammal, for instance, passes through stages at which the lower vertebrates remain fixed. All are therefore pursuing a journey along the same road, though some may travel to a longer, some to a shorter, distance. There is thus a parallelism between individual and race development; a close connection between the phases of development in the individual and in the species.

The type of each animal is from the first as it were imbedded in the embryo and controls its evolvement. The embryo never makes any attempt to change from one type to another, but sometimes the tendency to a form and not the form itself is transmitted.

The parallelism that exists between the career of the individual and the career of the race reappears in the life of the world. There is a resemblance—indeed more than a resemblance—between the successive forms through which man himself in his prenatal life has passed, and those that have appeared in myriads of ages in the biography of the earth. Common-sense revolts against the idea that these transformations are in the individual due to divine intervention. In that, and in the case of the earth, they must be due to natural law.

In the year 1859 there was published by Mr. Darwin a work on "The Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life."

In this, and in other subsequent works, it is shown that the individuals of each species tend to increase in a very rapid ratio—an increase more rapid than that of their means of subsistence. Each has, therefore, to contend with his competitors; and hence all must exhibit "a struggle for existence."

But modifications are incessantly taking place in the form and characteristics of individuals, giving to some an advantage, to some a disadvantage, as compared with their competitors. Hence, the former will prevail, the latter will succumb in the struggle. This in the language of the hypothesis is formulated "the survival of the fittest."

And as the pigeon-fancier or other person who devotes himself to the breeding of animals can produce any form he wishes by selecting its progenitors and pairing them together, exercising thus artificial selection, so if any of the chance-forms that have arisen should be better adapted than others for perpetuation, they will be perpetuated, or Nature may be said to have made a selection. Hence the term "natural selection," which has been made to designate this hypothesis.