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ologist, 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. Without much doubt the Poduras are the lowest of the six-footed insects. They are more embryonic in their appearance than others, as seen in the large size of the head compared with the rest of the body, the large, clumsy legs, and the equality in the size of the several segments composing the body. In other characters, such as the want of compound eyes, the absence of wings, the absence of a complete ovipositor, and the occasional want of tracheae, they stand at the base of the insect series. That they are true insects, however, we endeavored to show in the previous chapter, and that they are neuropterous, we think is most probable, since not only in the structure of the insect after birth do they agree with the larvae of certain neuropters, but, as we have shown in another place[14] in comparing the development of Isotoma, a Poduran, with that of a species of Caddis fly, the correspondence throughout the different embryological stages, nearly up to the time of hatching, is very striking. And it is a remarkable fact, as we have previously noticed, that when it begins to differ from the Caddis fly embryo, it begins to assume the Poduran characters, and its development consequently in some degree retrogrades, just as in the lice previous to hatching, as we have shown in a previous chapter, so that I think we are warranted at present in regarding the Thysanura, and especially the family of Podarids as degraded neuropters. Consequently
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