Again, going back of the larval period, and studying the insect in the egg, we find that nearly all the insects yet observed agree most strikingly in their mode of growth, so that, for instance, the earlier stages of the germ of a bee, fly or beetle, bear a remarkable resemblance to each other, and suggest again, more forcibly than when we examine the larval condition, that a common design or pattern at first pervades all. In the light of the studies of Von Baer, of Lamarck and Darwin, should we be content to stop here, or does this ideal archetype become endowed with life and have a definite existence, becoming the ancestral form of all insects, the prototype which gave birth to the hundreds of thousands of insect forms which are now spread over our globe, just as we see daily happens where a single aphis may become the progenitor of a million offspring clustering on the same tree? Is there not something more than analogy in the two things, and is not the same life-giving force that evolves a million young Aphides from the germ stock of a single Aphis in a single season, the same in kind with the production of the living races of insects from a primeval ancestor? When we see the Aphis giving origin in one season to successive generations, the individuals of which may be counted by the million, it is no less mysterious than that other succession of forms of insect life which has peopled the globe during the successive chapters of its history. While we see in one case the origin of individual forms, and cannot explain what it is that starts the life in the germ and so unerringly guides the course of the growing embryo, it is illogical to deny that the same life-giving force is concerned in the production of specific and generic forms.
185. Female Stylops.
Who can explain the origin of the sexes? What is the cause that determines that one individual in a brood of Stylops, for example (Fig. 184, male; Fig. 185, grub-like female in the body of its host), shall be but a grub, living as a parasite in the body of its host, while its fellow shall be winged and as free in its actions as the most highly organized insect? It is no less mysterious, because it daily occurs before our eyes. So perhaps none the less mysterious, and no more discordant with known natural laws may the law that governs the origin of species seem to those who come after us. Certainly the present attempts to discover that law, however fatuitous they may seem to many, are neither illogical, nor, judging by the impetus already given to biology, or the science of life, labor altogether spent in vain. The theory of evolution is a powerful tool, when judiciously used, that must eventually wrest many a secret from the grasp of nature.
But whether true or unproved, the theory of evolution in some shape has actually been adopted by the large proportion of naturalists, who find it indispensable in their researches, and it will be used until found inadequate to explain facts. Notwithstanding the present distrust, and even fear, with which it is received by many, we doubt not but that in comparatively few years all will acknowledge that the theory of evolution will be to biology what the nebular hypothesis is to geology, or the atomic theory is to chemistry. While the evolution theory is as yet imperfect, and many objections, some seemingly insuperable, can be raised against it, it should be borne in mind that the nebular hypothesis is still comparatively crude and unsatisfactory, though indispensable as a working theory to the geologist; and in chemistry, though the atomic theory may not be satisfactorily demonstrated to some minds until an atom is actually brought to sight, it is yet invaluable in research.
Many short sighted persons complain that such a theory sets in the back-ground the idea of a personal Creator; but minds no less devout, and perhaps a trifle more thoughtful, see the hand of a Creator not less in the evolution of plants and animals from prëexistent forms, through natural laws, than in the evolution of a summer's shower, through the laws discovered by the meteorologist, who looks back through myriads of ages to the causes that led to the distribution of mountain chains, ocean currents and trade winds, which combine to produce the necessary conditions resulting in that shower.
Indeed, to the student of nature, the evolution theory in biology, with the nebular hypothesis, and the grand law in physics of the correlation of forces, all interdependent, and revealing to us the mode in which the Creator of the Universe works in the world of matter, together form an immeasurably grander conception of the order of creation and its Ordainer, than was possible for us to form before these laws were discovered and put to practical use. We may be allowed, then, in a reverent spirit of inquiry, to attempt to trace the ancestry of the insects, and without arriving, perhaps, at any certain result, for it is largely a matter of speculation, point out certain facts, the thoughtful consideration of which may throw light on this difficult and embarrassing question.
186. Embryo of Diplax.
