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ferous scorpion (Buthus?) closely resembling a species now living in California, together with another scorpion-like animal, Mazonia Woodiana, while the Devonian insects described from St. John by Mr. Scudder, are nearly as highly organized as our grasshoppers and May flies. Dr. Dawson has also discovered a well developed milleped (Xylobius) in the Lower Coal Measures of Nova Scotia; so that we must go back to the Silurian period in our search for the earliest ancestor, or (if not of Darwinian proclivities) prototype, of insects." Afterwards[21] the writer, carrying out the idea suggested above, "referred the ancestry of the Myriopods, Arachnids, and Hexapodous insects to a Leptus-like terrestrial animal, bearing a vague resemblance to the Nauplius form among Crustacea, inasmuch as the body is not differentiated into a head, thorax and abdomen [though the head may be free from the rest of the body] and there are three pairs of temporary locomotive appendages. Like Nauplius, which was first supposed to be an adult Entomostracan, the larval form of Trombidium had been described as a genus of mites under the name of Leptus (also Ocypete and Astoma) and was supposed to be adult." In the same year Sir John Lubbock[22] agrees with Brauer that the groups represented by Podura and Campodea may have been the ancestors of the insects, remarking that "the genus Campodea must be regarded as a form of remarkable interest, since it is the living representative of a primaeval type from which not only the Collembola (Podura, etc.) and Thysanura, but the other great orders of insects, have all derived their origin." The comparison of the Leptus with the Nauplius, or pre-Zoeal stage of Crustacea, is much more natural. But here we are met with apparently insuperable difficulties. While the Nauplius (Fig. 191) has but three pairs of appendages, which become the two pairs of antennae and succeeding pair of limbs of the adult, in the Leptus as the least number we have five pairs, two of which belong to the head (the maxillae and mandibles) and three to the thorax; besides these is a true heed, distinct from the hinder region of the body. It is evident that the Leptus fundamentally differs from the Nauplius and begins life on a higher plane. We reject, therefore, the Crustacean origin of the insects. Our only refuge is in the worms, and how to account for the transmutation of any worm with which we are at present acquainted into a form
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